TIPS FOR CRAFTSMEN ON THE WORKING OF BONE & IVORY
The purpose of this treatise is to convey information to fellow craftsmen, artisans and individuals about the unique properties of bone, horn, Elforyn, Resin Ivory™ and ivory and to convey methods and procedures for successfully working these materials. These are unique materials and there are methods of working them that will help one avoid the problems that are all too often encountered by artisans who are not aware of their properties.
Part I, seen below, will address what most folks need to know and Part II will yield expanded information that will address ivory working by itself in detail. Some of this information is from our own knowledge of working these materials while some of the information is gleaned from Victorian, Colonial, Medieval and Ancient sources.
If you are buying bridge pins you need not know any of this information - an installation instruction sheet comes with the pins.
Use safety glasses, respirators, and other safety equipment when working with these materials. While these materials are not known or suspected carcinogens or other type of safety hazards they are dusty materials and can cause irritation to the lungs, etc. and can pose dangers such as splinters, chips flying, etc. just as woods do. When working with bone and ivory it is not necessary to use carbide tools. These materials cut well with a band saw and respond well to filing and sanding. The complete shaping of guitar nuts and saddles can be accomplished with the use of a hand saw , files and sandpaper. Folks making nuts and saddles will find a great ally in the 4" X 36 " mini-belt sanders found in home improvement stores as this tool and/or drum sanders in a drill press at high speed will reduce the amount of filing and hand sanding needed to shape these parts.
Bone & Ivory
When finishing up bone or ivory parts one should do the final sanding with wet/dry sandpaper and always use it dry. Garnet sandpaper is okay for rough shaping of the parts but the final work needs to be done with wet/dry paper. We recommend using a 120 garnet followed by a 220 wet/dry and then an old 220 and then 0000 steel wool. Bone and ivory parts should then be polished for two reasons - this gives them added beauty and, in the case of nuts and saddles, will actually improve the tone of the instrument. Polishing can be done by hand buffing with a good paste wax or by buffing on a buffing wheel with white jewelers rouge. In the case of hand polishing it is surprising how much of a shine can be developed in just a minute with a T shirt type material and paste wax. This works well on all four materials - bone, Ancient Mammoth ivory, Fossil Walrus and pre -ban Elephant ivory. Please note to never get FMI wet (except when bending violin-cello-bass bow tips) as it will warp, blister, erupt, bulge, etc.. A helpful sanding tip - take a piece of 1/8 inch thick Masonite type hardboard and cut it to a 1" X 9" stick. Then put 1 inch wide double-face tape on this stick and then apply wet/dry 220X paper to the tape. This gives the sandpaper some cushioning that allows for a smooth ride and a comfortable ride in sanding ivory, bone, etc.. For firmer sanding you can just glue the sandpaper to the stick itself.
When working Elforyn you will find that the higher the sandpaper grit you move up to the higher the gloss will be when buffed. A 200 to 400 grit will yield a matt gloss finish. If you go to 2000 grit you will enable the material to take a high gloss buffed finish.
RESIN IVORY™ cuts with standard wood and metal cutting band saw blades running at standard wood speed. This material machines well at high speeds with carbon steel tooling. Tools need to be sharp and if they are sharp you will have no chipping. If chipping occurs you need resharpened or new tooling. This is especially true of cue turning where lathes are fitted with high speed routers - if the router blades are sharp you will have no problem. Sanding is best done with wet/dry sandpaper with some artisans prefering wet while others prefer dry. I recommend dry.
At high turning speeds the Resin Ivory™ can burnish from sanding. This will result in burnishing the materials' surface and loading the sandpaper and micro-mesh with dust. Sanding can be done at high speeds with care or the speed can be lowered for more carefree sanding.
Polishing is done the same as ivory by buffing with white jewelers rouge on cloth or felt wheels. Lathe buffing can be done by applying rouge to the material after sanding and then holding a felt pad to the material. The rouge application and the felt pad buffing is best done at high speeds (1800 + RPM is what I work this material at for turning and buffing but I am sure that lower speeds will work well also). The material takes a very high buffed finish resulting in a very high gloss that looks just like real ivory.
Resin Ivory™ also accepts any clear coat finish with no resistance and no proclivity to peeling, etc.. I recommend a buffed finish wherever possible over the clear coat finish.
This material glues to wood with white glue or standard wood glues and to other materials with epoxies and super glues.
Resin Ivory also scrimshaws just like real ivory does. It does not have any negative scrim features. The ink sets fast - just like with real ivory and it will not bleed into unwanted areas.
Horn of any kind is technically matted hair and has shown itself to be unstable until one stabilizes it. Stabilizing is best done by clamping a slab of horn to a bar of steel or between two bars of steel and placing in the oven at 150 degrees for 30 to 45 minutes. Remove, let cool for several hours, and then do it again.
PART II Expanded/Detailed Information
Ivory is a great material and it works well with saws, files and sandpaper and it turns beautifully on a lathe. Files and sandpaper are very useful in the hand working of the material. Dremel cutters and polishing wheels are used by many folks with great success. One should avoid temperature and humidity swings with ivory. Ivory will crack and check if the atmospheric conditions are not stable. It is best to keep ivory at a comfortable human temperature and at 40% humidity. Craftsmen should purchase a humidifier for their work area should they desire to work ivory with success in dry climates.
Ivory has grain much like wood but it has the density of a soft metal. The material needs to be aged and seasoned. The material I sell is pre-ban ivory that is well seasoned. We also cut ivory properly - an art that is virtually gone in America today. Ivory grows in rings much like a tree and will crack and break up, over time, oftentimes in the rings it grew in, should it be improperly cut. When ivory is cut there is a great deal of waste and when it is cut properly there is a huge amount of waste. If you buy ivory from us, you can be assured it was cut properly so it will continue to age and season out in a manner that will not lead to the material breaking up over time. This is why we ask what the application of your ivory is. Ivory needs to be cut differently in accordance with the end application of that particular piece of ivory.
Keeping Ivory from Cracking:
Ivory is a pleasure to cut, drill, sand, and polish but the following information should be of help in these areas.
It is best to work ivory in 40% humidity environments and higher. This is especially important when dealing with larger diameter ivory items such as cue stick parts and hidden tang knife handle blocks. Slab ivory is not nearly as critical in regards to this and thin inlay material is seldom affected by lower moisture. Ivory gives and takes moisture even after centuries. The ivory you receive from us is aged and stable material but because ivory gives and takes moisture it will crack if it loses too much moisture too soon so this is why re-sealing the ivory is important as you work it, and then sealing it when the item is complete with a buffed finish or a clear coat finish.
When ivory is worked it is best to reseal the material, especially the end grain on large pieces, to keep it from checking and cracking. Resealing can be done with a coat of Elmers’ white glue set to dry or, most easily, by spraying the ivory liberally with any good clear coat finish. This resealing of the ivory is done when you plan on setting the partially worked ivory to the side for a day or two. After the ivory is sanded and properly polished you will no longer need to reseal the material. If your shop has good humidity it is not so important to reseal the ivory as you progress with your work although I still recommend doing so. I also recommend re-sealing the ivory as soon as is feasible in your work schedule. This is not something you say you will do when you get back from lunch. It is something you do as soon as you can. The smaller the ivory is, the less important resealing is. Piano keys are thin enough to breathe and never need any sealing. Slabs at 3/16" thick and less are pretty safe and should not need sealing. The same is true with guitar nuts and saddles, etc. but thicker knife handles, gun grips, etc. need attention in these areas. See also, information under cue sticks.
In any application where the ivory is placed next to a metal, such as in knife making where the ivory handle butts up against metal bolsters, it is important to put a coat or several coats of superglue on the end grain to help seal it from the effects of heat caused by polishing the metal when the knife is in the finishing stages. Heat, entering the ivory from the end grain can cause cracking. Use the superglue on the end grain prior to applying the handle. When buffing the knife try to not over buff the metal as the heat will travel into the ivory. If possible, buff in a high moisture environment - 40% or more humidity. See also, information under cue sticks for more info on sealing ivory to keep it from cracking.
When you need to bend ivory as when applying violin bow tips you just toss them into hot tap water for 20 minutes and then set them in a press to dry in shape. If it is a home made press you should use acrylic or Corian or other materials that will not color or otherwise affect the soft and wet ivory. Wood will lend the parts a discoloration as will some metals. The bow tips should be left to dry for 15 hours or so and then you should have the shape you need. Note that tips arrive as a rectangle and the finished shape is that of a curvy "V'. To aid bending significantly you should remove as much of the material that is not needed as possible such that what you soak in the hot water is already a slightly oversize "V".
In the case of guitar binding there is much to know. Use scarf joints rather than butt joints. Our binding material comes S2S and those are the sides to be glued down. It is best to throw the pre-scarfed strips into hot tap water and let them there for 2 hours or more. The water will cool but that is okay. If you can use distilled water that is better yet as it has a greater effect upon the ivory. Now comes the hard part. You need to take it out and glue it to your guitar in a neat and tidy fashion with crisp scarf joinery. Best to use hide glue and you will need lots of clamps and patience. I have never done this and I shudder at the thought of doing it but we have sold binding to a lot of guys and girls over many years and they have all reported back with great success. It is important to buy the binding as small as you can possibly buy it. We cut to within a few thousandths of an inch so you can order it small. Every thousandth makes a big difference in its pliability in this application. See also the expanded information on bending ivory further below.
Piano Key Application:
I cannot stress enough to have a professional do this if you need a complete set done. There are qualified men and women in America who apply ivory key tops professionally - take advantage of their skills. If you want to do it yourself or if you just have a few keys to repair then here are some tips - read them all before you start. Use glue wafers (available from piano repair supply houses - a web search should find them) with additional glue. If you just have a few keys to do you can use white card stock paper in lieu of the glue wafers. If doing a few keys then use Elmer's, white glue - oftentimes called " Glue-All " - this is the white glue not the yellow wood glue. Prepare the key top surface and glue the white card stock paper to it. After 24 hours glue the ivory or bone down , clamp for 48 + hours. You need to have a clamp that is a plate or is holding a plate of metal against the entire surface of the part being glued. If you are gluing down a 1 inch by 2 inch piano head then the brass or metal plate needs to be this size. This ivory is dry so a metal plate will not bleed color into the material. After 48 hours of drying remove clamps, sand and polish (sanding and polishing techniques mentioned in an above paragraph. The joints on two piece key tops is scarfed at a slight angle - we sell them at 90 degree cuts and you need to scarf them yourself or use the butt joint. Either way they need to be prepared by you for joinery. If you are doing a two piece top then glue the tail down first and after it is completely done (48 hours of drying) then apply the head. Now, if you want to do an entire set then, again, consider having a professional do it. If you still wish to proceed then you need to know it is best to use a 55 % PVA glue. This is a beefed up version of Elmer's but it is hard to find. At times we sell it - email for details through our contact page. It is $ 15 for a pint squeeze bottle and we have to charge more than $ 6 for shipping as it costs quite a bit to ship. Use the glue wafers as well. This is another operation I would hate to do without all the proper clamps and jigs the pros' have but I have to admit we have sold a lot of key top sets to folks doing it themselves for the first time and their results have been good.
Inlay slabs for cue stick applications do not need sealing but the round cue parts do. Ferrules are not so critical but joint stock and butt cap stock are prone to cracking and checking in a dry environment. Top-notch cue makers reseal the ivory during the various stages of cue production - usually by applying a thin coat of Elmers’ white glue to the ivory as it spins. In the end, they work this coating off and very soon afterwards apply their finish coat to the cue and ivory. Do not use heat-lamps to help dry the finish as it will cause the ivory round stock to crack.
When making a cue joint section where the face of the ivory is purposefully left unsealed it is best to coat this face with a film of CA (superglue) glue. After it dries one should turn it, and, utilizing sandpaper or a burnishing tool, one needs to burnish the glued surface. This should be repeated 5 times. You will then have a micro-sealed surface of end grain ivory and this will hold up much better to atmospheric changes over the life of the cue stick.
If you do not have an atmospherically controlled workshop you may wish to work in the fair weather months when humidity is naturally high across much of the country. Folks living in southern States have little or no problems year-round and folks in the eastern half of the U.S. and west coast areas seldom have problems in the fair weather months. The dry western States are where folks really need a humidified shop as well as folks working ivory in the dry winter months in any area. Swings in temperature can also cause cracking especially if the swings are sudden as when one turns the heat or air-conditioning of a shop off for the night or weekend.
The shaping of ivory is accomplished with saws and files. Belt and drum sanders work well but one needs to take care the ivory is not heated up too much in this work as, again, checking can occur especially on the end grain. Many folks use Dremel type cutters to carve and shape the ivory - this is especially helpful when carving figurines and other "in the round" art. Keep ivory dry – that is – do not get ivory wet while working it. Hand sanding is best with a wet-dry type of sandpaper – use it dry. Final sanding is to be done with a used or "dead" 220X paper. When developing a buffed finish you will find a proper buffing procedure will remove all the scratches of a dead 220 sanding and leave your ivory with a mirror like surface.
Here is a short write-up presented by nationally known cue maker Chris Nitti on the process of applying an ivory cue ferrule :
How to make capped ivory ferrules. 1” length.
This is the method I use on a metal working lathe. It is assumed the operator has lathe experience.
5/16” center drill bit
1/8” drill bit
“F” drill bit (.257)
5/16 x 18 tap
.040” drill bit (may require pin vise)
1. Mount ferrule blank in chuck. Remove sealer if necessary for accurate turning.
2. Face off end of ferrule
3. Center drill starter hole
4. Using the 1/8” bit, drill ¾” deep. NOTE: When drilling ivory, I always drill halfway first then back out to remove the ivory on the drill bit. Failure to do this before proceeding will result in the ferrule overheating and causing cracks. I am also blowing compressed air during drilling for cooling. Do not leave the drill bits in the ferrule any longer than necessary.
5. Using the “F” drill bit, drill ¾” deep.
6. Install 5/16 x 18 tap in tailstock drill chuck. While turning lathe by hand, tap threads in ferrule.
7. Remove ferrule and reinstall with other end facing out.
8. Face off end of ferrule.
9. Using center drill bit make a small center to provide a start for the .040 drill bit. (barely touch)
10. Using .040” drill bit, drill thru to provide a “glue relief hole” to allow glue to escape when installing.
Polishing and Lathe Turning Ivory:
Polishing ivory is best done by buffing. I recommend utilizing a sewn wheel followed by a floppy wheel. A white jewelers rouge should be utilized. Small parts can be polished with small felt wheels set in a Dremel or drill press. When buffing on a lathe one will find that after a final sanding the rouge can be held to the turning ivory for a melt-on application followed by a burnishing of this rouge into the ivory with a thick piece of felt held to the ivory surface. The ivory will get hot but one develops a "feel" for how hot this can get before one experiences cracking or checking. Turning and polishing on a lathe should be done at about 2000 RPM.
Pen Making on a Lathe:
Ivory writing pens can crack if not turned and sealed properly. They can crack even if turned and sealed properly. If your pen blank arrives as a one piece blank it is best to cut it in two and work with each half separately. Most people seal the inside of the pens with a coating of superglue and they put a thin coat on the outside as well. The inside coat is applied and let to dry and even two coats might be a good idea. The outside layer is left to dry and then sanded down after the application and polished. I would recommend 2 or more coats on the outside with sanding between coats and then the final polish. If you have the patience, 5 coats would be best with sanding between each coat and then the final finish. I know of one maker who says he uses the superglue as a finish on the exterior but I am unsure of how he spreads it evenly and attains a final finish that is attractive. By doing the several coats of superglue you will then have a micro-sealed surface of ivory that will hold up much better to atmospheric changes over the life of the pen. Once a pen is made it is best not to have it sitting in direct sunlight or to place it in a situation where it is exposed to extreme temperatures such as in a car. Pen makers purchase scrap ivory to serve as accent and inlay pieces on wooden pens and this works out very well and you escape all of the fears of cracking "big ivory" by working in small ivory which is not problematic. Also, to help you with drilling the pens see below for information on drilling:
Drilling & Boring:
Drilling ivory oftentimes causes cracking. Drilling small holes for knife handle rivets, etc. are not a problem but large bore drilling for items like cue joints and butt caps are. When doing large bore drilling, it is best to drill a large pilot hole prior to the final size drilling (if and when possible and feasible). Boring bars or "gun drills" are better than standard drill bits because they do not develop as much heat. Regular drill bits can be used but one should drill short areas at a time and allow the bit to cool before reentering the ivory. It is the heat and pressure combined that cause the cracking. Lathe boring with a drill bit is best achieved by grinding down the diameter of the bit behind the cutting flukes. This allows for zero friction except where the cutting is being done at the tip of the drill bit. If you are making a pen in two pieces or any part in pieces it is best to cut the ivory to length before boring, etc. so if it cracks you are only losing the part you are boring rather than the entire rod.
Finished ivory should not get wet (water) and should be kept from extended periods of direct or indirect sunlight. In the winter or dry times some folks keep a film of mineral oil on their knife handles or other finished ivory work and this is not a bad idea. Do not apply a thick coat but rather just a light film as this will keep it from cracking in the dry months. This needs to be done only for a few years after the item is made - by then the material is stable enough to not need it however we recommend that most utility items such as knife handles, gun grips, cane handles, etc. be waxed with Renaissance wax once a year or so.
Ivory inlays in wood need special attention. When ivory is thinner than .085 " it has a translucency factor that will cause the inlays to appear darker. To alleviate this feature one should glue white card stock paper to the back of the inlay or apply this paper to the inlay socket that will be accepting the ivory inlay - this will lighten up the ivory to look whiter and more ivory-like in a dark wood. Once inlaid the ivory should be finished as you desire. If a hide glue is utilized one can add titanium dioxide to the glue so it will dry white (see glues, below). If the object is lacquered then just lacquer over the ivory just as you do the wood. Use a non-yellowing finish as yellowing will affect the beauty of the ivory long before noticed on the wood. If the object is buffed then you will find the ivory will buff nicely. Also, see my information about glues - below.
Dyeing and Aging of Ivory:
Dyeing ivory can be accomplished by using any of a variety of dyestuffs. The ivory must be brought to a high polish prior to dyeing. The ivory should be "mordanted" by immersing the ivory in muriatic acid for 15 to 20 seconds prior to the immersion into the hot dye. SAFETY NOTE: This procedure utilizes acid. Always wear eye protection and plastic or latex gloves when handling acids. Also, always pour acid into water and never water into acid. Pouring water into acid can cause a boiling and splashing reaction.
The dye should be hot but not boiling. After removing the ivory from the dye, the color will darken a shade or two. After drying the dyed ivory carefully by patting the item dry rather than wiping the object dry, let it cool for an hour or so and then rebuff to bring up the high polish again. Be careful not to rebuff too harshly on a firm wheel (sewn) or the color will be buffed out of high areas. This final buffing is best done on a floppy wheel. You can make ivory any color or black and all with a very high gloss that will rival any plastic or acrylic for brightness and boldness of color.
Aging of ivory is done through many techniques. The simplest and most commonly used technique is to polish the ivory to a high gloss and then immerse the ivory in a container of hot tea. The tea should be very hot but not boiling. The tea should have a tablespoon of white vinegar per cup of tea to serve as a mordant. Removing the ivory from the tea , one should let cool and then buff. Follow similar cautions as seen in dyeing paragraph above. Ivory can also be put on a cookie sheet in a conventional oven at 150 degrees to achieve crazing and color - experiment at your own risk - best to crack the oven doors at all times.
Scrimshaw - the art of ivory engraving is a simple and easy to learn art form. One needs to polish the ivory to a high gloss by buffing. The ivory is then scored or scratched with a sharp needle or knife point and black India ink is applied to the surface. It takes about 30 seconds for the ink to dry and then the excess ink is wiped from the ivory with a cloth dampened with spit. Water is too watery and oils are too oily - spit works best ! I apply the ink with a q-tip and I prefer Koh-I-Noor brand ink. A good friend of mine does excellent scrimshaw and utilizes only # 16 x-acto blades ! I prefer a needle point which I fashion on the back end of a # 48 drill bit. I hold the bit in a mechanical pencil and a number 48 bit works well as it is the same diameter as the lead for the pencil. Templates can be made from thin plastic found in art and graphic supply stores - this material is known as acetate and I find .010 thickness works well. We also sell a great scrimshaw kit on this website.
Bleaching ivory can be achieved in several ways. The best method is to immerse the ivory object in 30 % to 40 % Hydrogen-Peroxide (H2O2) for 4 days, rinse in warm water, and then set the item out to dry. Be aware this is a tricky process.When setting out to dry, place items such as thin slabs, etc. in a rack of some sort so they do not lay flat. They must not dry while touching a colored material such as wood or metal. It is best to have them dry against white or light colored Corian, acrylic or other inert and non colored material. Be aware not to bleach a finished part - this is a process to bleach ivory stock. Once white and properly dried it can then be worked into a finished product. The ivory will end up being very white but this process can cause cracking and other problems. This is a process not recommended for folks who are just learning about ivory and I caution seasoned veterans of the material as well. There are many little aspects to know that would lengthen this treatise three-fold by simply expanding upon this one topic.
Telling Real Ivory from bone or plastic:
Real ivory can be discerned from imitation ivory by looking on the end grain of the object in question. Real ivory (elephant) has a herringbone design within the grain itself whereas imitation ivories have not been able to replicate this design.
Also, a wood burning kit - like the ones' kids' get for Christmas - will melt plastic but not bone or ivory. These tests can help determine if your object is ivory or likely to be ivory but sometimes it is difficult for even the most trained individual to tell the difference between ivory, bone, and the imitations.
Gluing ivory and finding the right glue can be problematic. Ivory has a creamy texture and, on a molecular scale, it is oily - hence it does not like to be glued. Elmer’s white glue works in many applications. Epoxy glues seem to work well in most inlays into flat grain wood but they tend to push ivory out in side grain applications. CA glues work great if the ivory and its counterpart are very smooth flat surfaces - we just do not know the life span of CA. For most applications I use a 55% PVA resin glue (high strength white glue - it is like Elmer's Glue-all on steroids). In most applications one needs to clamp the ivory while gluing because the moisture in the glue will cup and pull the ivory until the moisture in the glue has flashed off. Clamp for 48 or more hours. Hide glue and fish glue work well. Titanium dioxide added as a whitener will allow the glue to dry white, thus aiding thin ivory applications with the age-old problem of translucency.
Please note - sealing the end grain of ivory with super glue (several coats) is an excellent way of protecting the ivory from cracking. This is most applicable to cue joint faces and to knife handles, especially where the ivory is fitted up against metal bolsters as the bolsters get hot during buffing and send heat into the ivory causing cracking. The CA glue will help as will caution and speed control of buffing.
Bending and molding ivory has been an age old quest. When ivory is small - as in guitar binding, one can simply soak it in distilled water for a few hours or perhaps a day and then bend it and force it into the application with hand force and then keep it there with clamps until the glue is dry. Best to utilize hide glue in this type application and best to utilize a scarf joint rather than a butt joint where the ivory strips meet. To make tighter bends or easier bends one can soak the binding in white vinegar for 3 to 4 hours. This action will render the ivory extremely pliable. Glue it into its new shape and position right after removing it from the vinegar and allow 48 hours minimum glue drying time before removing clamps, etc.. Sand the ivory to desired trim and final shape but do not finish for one + week. After that time has lapsed you should re-sand the binding and apply your finish. Note that after the vinegar soak the ivory will look mottled and discolored, so much so as to lose heart, but after sanding, drying, and re-sanding the ivory will return to its pre-soak beauty and appearance. Most bending requirements of ivory, even larger than binding size ivory applications, can be achieved with ease via the vinegar soak. The next step in bending of larger pieces can be achieved with bo-peep ammonia. Follow same instructions as with vinegar but note that ammonia will affect the ivory by discoloring it and causing a mottled appearance. With vinegar this goes away but with ammonia it usually stays - sometimes it will go away. If it stays - it will look old-time and antiqued so if you are restoring an antique then you have no worries. Use the ammonia only if you find the water or vinegar methods do not yield the pliability you are needful of. Use the ancient methods given below only if you must or if you love to try little experiments, etc. as you plow through life.
As to the ancient methods for softening, forming, and re-hardening elephant ivory, most of the older books read almost identically to this typical entry from "The Scientific American Cyclopedia of Receipts, Notes, and Queries", edited by Albert A. Hopkins, published by Munn & Co., 1892, page 290:
Ivory, to soften:
1.) In 3 oz. of spirits of nitre, and 15 of water, mixed, put the ivory and leave for three or four days.
2.) To make Ivory Soft and Flexible. -- Take a solution of phosphoric acid of 1.130 sp. gr. Put the ivory in this solution, and let it remain until it has a transparent appearance. Take out, wash carefully, dry between soft linen. The ivory will be soft as thick leather. It will become hard if it is exposed to the air, but become soft again if placed in warm water.
Here is a copyrighted treatise from Master Scrimshaw Artist Jim Stevens on the softening and re-hardening of ivory :
Softening and Hardening Ivory
By Jim Stevens © 2011
Each piece of ivory has its own reactive potential and therefore the following information is for informational purposes only and is offered without warranties or guarantees of any kind. The information presented here is based solely on Mr. Stevens own testing and experience.
SAFETY NOTE: This procedure utilizes phosphoric acid. Always wear eye protection and plastic or latex gloves when handling acids. Also, always pour acid into water and never water into acid. Pouring water into acid can cause a boiling and splashing reaction.
Make a solution of water and phosphoric acid with a combined specific gravity of 1.130. You will need a hydrometer and a hydrometer test jar (tube) for this procedure.
Let the ivory soak in this solution until it loses its opaqueness and takes on a semi-transparent or translucent appearance.
If soaking a thin panel, the ivory may want to curl. Prevent this by placing a weight, like a heavy clear drinking glass, on the ivory while it soaks.
Remove from the solution and wash thoroughly in clean cold water to stop the acid reaction and then dry it off.
Ivory will be flexible and possess the approximate hardness of thick leather.
The ivory will gradually harden with exposure to the air, but immersion in simmering hot water will restore its softness and flexibility as long as the ivory has not been properly dried yet in decrepitated salt.
Actual effects of this procedure:
The following information is based on a 1/16th inch thick panel of ivory that is 1 ½” wide and 2 ½” long. Variations will exist for ivory pieces at different thicknesses and sizes, though the variations will be minor unless the ivory is very thick.
A 1/16th inch thick panel of ivory soaked for 5 hours becomes flexible enough to wrap around a 1/16th inch diameter rod. Soaked for 7 hours, the ivory is so flexible, it can actually be folded back onto itself without splitting.
Ivory soaked for 5 hours reacts to carving tools like thick soggy leather and spreads badly as the carving tools are pressed into or through it. For carving purposes, soaking for only 2-to-3 hours softens the ivory but leaves enough strength in the ivory structure for more accurate carving with less “spreading” of the ivory as the tool pushes into or through the material.
Any serious softening will cause the ivory to spread at least a little under the pressure of a carving tool, so care does need to be taken when carving softened ivory. Softening an ivory surface slightly by using a little water is more often a method used for carving as it does not cause the ivory to spread under tools and if dried right away, will usually cause no permanent damage to the internal structure of the ivory.
After soaking, the ivory retains its softness and flexibility for approximately 24 hours before it starts to stiffen. At the end of that 24-hour period, the ivory will still not be hard and remains flexible, just not quite as flexible as it was right after soaking. It remains flexible and simply does not regain its original hardness and structural integrity until after it is dried in decrepitated salt for at least 24 hours. It can take up to 48 hours to harden completely if the ivory was soaked for a more extended period of time.
Drying Ivory After Softening
To restore ivory to its original color and hardness after softening, wrap the ivory in a sheet of white paper and cover it with dry, decrepitated salt and let it set covered for 24-to-48 hours, depending on how long the ivory was soaked.
Clamp thin panels of ivory wrapped in paper between flat pieces of wood or other stiff material while drying to keep the ivory from re-hardening in wavy curves.
Making decrepitated salt:
Spread common table salt out on a baking pan and dry it at very low heat in the kitchen oven until it loses its crystal appearance and takes on a dense opaque white look. Since this method takes a while, leave the oven door open to prevent the oven from getting too hot inside and burning the salt.
Spread a 1/2" deep layer of Epsom Salt out on a baking pan. Bake in the kitchen oven at 400 degrees Fahrenheit for an hour and it will lose half its water content and be as good as dried table salt as a desiccant.
At 480 F for two hours the Epsom Salt will lose virtually all its water weight and becomes one of the best desiccants available.
Put into fine-weave cloth bags, or sealed containers. Remove as much air as possible from the containers when sealing or closing. Weigh your full containers. When the containers gain 25-to- 50% more than their original weight, the salt has rehydrated and it is time to recharge the Epsom Salt’s desiccating ability by baking it again.
SAFETY NOTE: All Epsom Salt you buy is fully hydrated. The reason is because if you add water to dried Epsom Salt, the salt will get VERY HOT. So be careful to not spill water on it or place it in direct contact with wet ivory. Its is important to dry your ivory very well before wrapping it in white paper and covering it with the dried Epsom Salt.
Of interest :
"Ivory and the Elephant: In Art, In Archeology and In Science", George Frederick Kunz, 1916, p.243:
Very thin, pliant veneers have been cut into spirals out of a solid block of ivory by means of a feather-edged veneer saw, and some years ago a Monsieur Page patented a process for such work. He produced pieces 17 by 38 in., and asserted that he could make much larger pieces, up to 30 by 50 in. The excessive thinness -- 1/50 in. (note: = .020") -- and the transparency of this veneer renders it not very well adapted for application to wood, etc., as the material beneath would show through to a certain extent. As material for the painter's art, however, it might answer better.
Charles Holtzapffel, in "Turning & Mechanical Manipulation", 1846 (published 10 years before Kunz was born), Vol. I "Materials", p.154 footnote, while also mentioning this same method of producing thin sheets indicates that they had been somewhat thicker than that referred to by Kunz (Kunz' M. "Page" and Holtzapffel's M. "Pape" are obviously one and the same person, with the latter spelling probably being correct since it appears twice and predates the Kunz reference):
Monsieur H. Pape, of Paris, piano-forte manufacturer, has taken out patents for this method of cutting ivory spirally into sheets. A specimen, 17 inches by 38 inches, and about one thirtieth of an inch thick (note: = .033", slightly over 1/32"), glued upon a board, may be seen at the Polytechnic Exhibition in Regent-street, and M. Pape advertises to supply sheets as large as 30 by 150 inches (note: this must be a misprint, as 150" would exceed the workable length of even the largest tusks; probably Kunz' 50 inches is the correct number). He has veneered a piano-forte entirely with ivory. Similar veneers of ivory are now also cut in England.
I would suggest that much thicker sheets could be produced if the tusk section (or at least the material on its outer surface) was first softened before being cut. As support for this idea, Kunz also mentions the impossibly large pieces found in some very ancient statuary (pp.22-23):
The very large size of the pieces of ivory which must have been required by the Greeks in the production of their colossal gold and ivory statues, some of which were forty feet or more in height, the face, hands, and feet being of ivory, and even the large size of some of the consular and other diptychs that have come down to us, have raised the question, how did the ancients secure pieces of ivory of sufficient size? In our day, with the processes now in use, this would not be possible. Hence it has been conjectured that they possessed some lost art for welding together separate pieces of ivory. In the late Latin treatise on the arts of the Romans, belonging to the tenth century, and which passes under the name of Eraclius, the following directions are given: "Take sulphate of potash, fossil salt, and vitriol; these are ground up with very sharp vinegar in a brass mortar. Into the mixture the ivory is placed for three days and nights. This being done, you will hollow into a piece of wood as you please. The ivory being thus placed in the hollow, you direct it and will bend it to your will." But this recipe as well as others given by various ancient writers do not give satisfactory experimental results.
Although in some instances tusks of quite exceptional size have furnished very large flat pieces of ivory, it is regarded as possible, if not probable, that the ancients cut large cylindrical pieces from the median part of the tusk, split these cylinders at a given point, softened them by some process, and then flattened them out, thus securing a piece as broad as the circumference of the tusk. This theory was advanced by Mons. Quatremere de Quincy. Steeping in vinegar and almond oil does really render ivory ductile to a certain extent. While it can be decomposed by caustic alkalis, it cannot be recomposed.
In all of your work with ivory utilize proper safety precautions - eye protection, respirators, etc..
There are many old wives tales on how to care for ivory and most are simply not effective or applicable to most ivory items. Ivory piano and organ keys can be cleaned with milk - it works well - followed by a wiping down with bathroom alcohol. Piano keys are the only thing I can think of that could best utilize the application of milk as a cleanser.
Knife handles and gun grips and other smooth ivory objects can best be cleaned with alcohol. Q-tips are good for this and even a toothbrush. Once cleaned, I recommend a waxing with a good paste wax. I like "Renaissance wax" from England. While expensive, one jar will wax everything a man owns for the rest of his life.
Carved items, where dirt has worked itself into recesses, can be cleaned with a soft toothbrush and alcohol. If the dirt is stubborn one can use toothpaste or soap and warm water however the polish is going to dull down with this method and so it is recommended only for those who can re-establish the polish via buffing. A light buffing on most items will bring the luster back quickly and with ease - still - proceed with caution.
Bleach (Chlorine) can be used to clean ivory but it is tricky in that it eats away at the ivory. Application and scrubbing needs to be done quickly in warm water and then rinsed thoroughly in a tub of vinegar water. The vinegar cuts the bleaching action. Be aware the bleach will also whiten the ivory and will destroy the polish so you will lose some or all of the aged patina the object holds and you will need to re-polish the object. Bleaching has its' place in but it is generally not recommended .
There are many people who believe that oils are good for ivory. Never use olive oil on ivory as it will permanently discolor the material and attract dirt and, eventually, bacteria. Never use oils in the working of ivory. Among knife makers there is an old wives' tale that speaks of immersing ivory in milk or oils before working it - save yourself a great deal of grief by discarding this crazy idea and never letting it re-enter your head.
After a smooth ivory object is completed and polished one can apply a thin coating of mineral oil. Mineral oil is sold as a laxative in most drug stores and comes in differing viscosities. I recommend thin or light mineral oil as opposed to heavy or thick. This is best for knife handles and gun grips and is especially applicable to newly worked ivory that is in a dry climate. It is oftentimes applied to such items as one enters wintertime in northern States. It is best to think of keeping a light film of this oil on the ivory just as one would keep a thin film of oil on a gun to keep it from rusting. This is not something that is needful forever. I usually recommend such treatment for the first few years after the item is made and then one can switch over to the Renaissance wax which is not as messy. Keep in mind - most folks need only concern themselves with this if they are in dry climates. When shipping ivory one can put a film of oil on the ivory and then wrap it in Saran wrap. This is a good idea as shipping involves temperature and humidity swings beyond measure - it is cold and dry at 30,000 feet in a cargo plane full of postal. The Saran wrap idea can also be used to keep ivory from cracking in dry winter months but you need to unwrap them and just leave a film of oil on them during fair weather (moister) months
Keeping moving air and direct sunlight away from ivory is a good idea. A curio cabinet is a good place to display ivory items as there is no moving air. In dry times one can place a cup of water in the cabinet to bring up the humidity with ease. Keep in mind , all of these precautions are for " big ivory " such as knife handles, gun grips, etc.. Items such as pool cue sticks are far less susceptible to needing this care because the ivory has not been buffed but has been sealed over with a clear finish - thus protecting it from the open air.
Knife handles, in particular, are subject to cracking from dry air moving over the surface of the ivory. It is best to display knives in a display case with a closeable lid so that they are not subject to moving air.
Given the precautions one would think ivory is not a desirable material but rather the opposite is true. Once an item is made of ivory, with minimal care, it will give long lasting beauty and joy to you . Given its' longevity you can expect a well made ivory item to last indefinitely. Archaeologists unearth ivory items with frequency that date back to the dawn of human civilization. The oldest known piece of artwork created by man was made of ancient mammoth ivory. The oldest known piece of artwork that depicts a human form is also of ivory. Man has been working ivory for tens of thousands of years. Ivory workers are normal - animal rights people are nuts. All cultures, ancient and modern, have utilized and treasured ivory and the Romans considered ivory to be the noblest of all materials on earth.
Dover , Ohio