I suspect many people, if not most, are familiar with Corian, a proprietary brand of countertop material manufactured by the DuPont Corporation that has been a feature of kitchens and bathrooms worldwide since its introduction in 1971, having first been made in 1967 and patented in 1968. A niche use of this material is in the making of custom pens, a use that many people may not have heard of despite the common knowledge of the material itself.
What is Corian Anyway?
Corian is technically described as an acrylic polymer mixed with alumina trihydrate. The alumina, as the name implies, is an aluminium (the spelling used by every country other than the United States and therefore, to my mind, more correct despite the complicity of the IUPAC in American obstreperousness) compound most commonly used as an ore for the production of pure aluminium metal. Acrylic polymer is a petroleum derivative that is best described in common terms as a “plastic” despite the potential howls of hardline chemists who would no doubt wish to muddy the waters of commonly understood terms in the pursuit of specificity that won’t mean anything to most of us anyway. In the sense of Corian being an acrylic of any sort, it is similar to the many other brands, descriptions, and formulations of acrylic pen blanks that custom pen makers are likely familiar with and which are commonly available from specialty retailers, although I find Corian to be far less brittle than most of the other “acrylic” pen blanks I have worked with and therefore, to my mind, easier to use.
The Diversity of Corian
Corian has the advantage of being available in a rainbow of colors, although few of the colors are actually solid, instead most often being designed to mimic other materials such as various types and colors of stone such as granite or marble, which are also highly desirable countertop materials, but options which come at a much higher price premium than Corian. At last count, Corian is available in over 100 different colorful designs and patterns, making a rich resource for custom pen making, easily rivaling the varieties of woods and even other plastics available to both the professional pen maker and the hobbyist, especially if a stone look is desired.
One of the downsides of Corian is that it is never produced in sizes any thicker than 19 millimeters, about 0.75 inch, although I have never seen samples of such width; instead I have only ever found the much more commonly produced 12 millimeter, about 0.47 inch, the size most commonly used for countertops. Reportedly, Corian is also produced in thicknesses of as little as 6 millimeters but I have never seen any material this thin. The commonly available 12 millimeter thickness severely limits the pen kits which can be used with Corian blanks. In fact, the only pen kit that I am aware of that will accommodate such size restrictions is the various kits that are all based on a 7 millimeter bore, sold under such names as “Slimline” as well as others depending on the retailer and/or manufacturer.
Some users have reportedly had success with gluing several smaller thickness blanks together to make thicker blanks but I fear that even if the glued blank were structurally sound that the bond line would be certain to show and thus mar the visual, and perhaps even the tactile, appeal of the finished product. More recently still, I have read about the availability of sheets of Corian material that some are using to make small platters, or very shallow bowls, as well as of users bonding several sheets together to make ever deeper bowls and other hollow forms. As is often the case, dedicated hobbyists will find ever increasing and unusual uses for materials originally intended for quite different purposes.
Regardless of what you call it, in my experience, Corian behaves very much like a plastic when it is being worked on the lathe and otherwise prepared for pen making and that fact requires some modifications to more standard procedures associated with wood blanks. Cutting the blanks to size doesn’t seem to require anything other than a standard sharp blade. Corian cuts quite cleanly although the cut edges will not be glossy until they are properly finished. The next step in making Corian pens is, of course, drilling out the center for the placement of the brass tubing and it is in this step that the most care must be taken, as is also commonly the case with other acrylic materials.
Any drilling action will result in friction which creates heat. While Corian is designed to be resistant to heat in its use as a countertop material, that doesn’t mean it is impervious to heat. Adequate heat creation, such as is generated from the friction associated with drilling processes, can and will melt or otherwise deform and weaken Corian to the point of breakage and failure. Therefore, it is important to use a relatively slow drill speed, never more than 600 RPM, along with a high quality drill bit to have the greatest possible degree of success.
Some years ago Colt Tools announced with some fanfare their high-end drill bits especially designed for pen makers. One of the advertised and promotional video demonstrated benefits of these specialty drill bits was the ability to drill the core of an acrylic pen blank in one pass with no need to intermittently withdraw the bit to ensure the clearance of material. I have a full range of these Colt pen making drill bits and I have experimented with them in this exact regard. I find it to be true that the Colt pen making drill bits cut cleanly and evacuate the waste material quite effectively without withdrawing repeatedly. However, this will only work if the pen maker is making ONLY ONE PEN AT A TIME! I personally never make only one pen at a time, instead I make them in batch production runs to justify the time and effort involved in setting up the special chucks, the gluing supplies and resultant mess, the end mills, and the special mandrels and bushings all needed to make either one pen or one hundred pens. For me, it simply isn’t worth the effort for a one off. That said, if you use a Colt pen making drill bit REPEATEDLY it will no longer be able to deliver the advertised performance! The bit will inevitably become quite hot, far too hot to touch, and that heat will result in the waste material softening, if not melting, and no longer evacuating the bore hole, which can cause your bit to seize up completely and ultimately to break your blank, or at the least go off of centerline in drilling. When drilling a 7 millimeter hole into a 12 millimeter square you have very little margin for error off the centerline. If you are making more than one pen at a time, you have to modify the advertised methods of using the Colt bits and if you are using a lower quality drill bit you should never attempt a single pass drilling of any acrylic material.
Along with a slow speed, carefully watch the material coming out of the bore hole with the drill bit. There should be constant and steady flow of material. I like to catch this material in my hand to check for heat. When the material is too hot to touch I know my bit is too hot. Also, if the material is not flowing out steadily and constantly it likely indicates that the waste is building up and gumming in the channels of the drill bit. These problems are almost certain to occur with lower quality drill bits but will also occur with quickly repeated use of even the highest end Colt pen making drill bits. One method to help prevent this problem is to intermittently withdraw the bit from the bore hole and let all the waste material clear, aiding this process with compressed air when necessary. But the single most effective means I have found to counteract the problem of heat buildup when working on a production run of drilling multiple blanks is to cool the drill bit between blanks.
Keeping It Cool
The means of cooling will vary depending on what method you use to drill your pen blanks. I know many people use a drill press for this process and if so, one method of cooling the bit is to immerse it into a jar or can of cold water between drilling. Personally, I use special centering chucks and drill my blanks on the lathe so I can’t use a container of water, so instead I use cloth towels soaked in cold water and stored in between uses in the freeze to wrap my drill bit with in between drilling. I have also used reusable cold packs out of the freezer to help avoid excess water dripping onto the lathe bed. It is very important to note that anytime water is used with drill bits, or anytime water comes into contact with the lathe bed, it MUST be thoroughly dried to avoid the possibility of rusting. Acetone, which is conveniently the same thing as super glue solvent, is readily and cheaply available in the paint section of any hardware or home improvement store (I suspect it is also sold in paint stores if those still exist) and acetone is an excellent drying agent commonly used in laboratory glassware where all traces of water must be removed. Simply dip your drill bits into acetone after contact with water. The acetone will wash away the water and the acetone itself rapidly evaporates, hence the cooling sensation on your skin, leaving the bits completely dry. You can also wipe exposed surfaces of your lathe bed with acetone on a paper towel, or I also use purpose made lathe bed conditioner sprays that remove grease, water, and other contaminants leaving the lathe bed lubricated and protected against moisture, which is helpful in general since I live in a humid climate.
One additional method I have used in conjunction with drill bit cooling is to cool the Corian blanks themselves by placing them in a household freezer for at least 24 hours before drilling. I have the good fortune to have a freezer located right in my shop area and I keep the blanks frozen until right before loading them into the chuck to drill them. The combination of cooled drill bits and frozen blanks work quite well to reduce the problems associated with overheating during drilling. I know it sounds strange, and it probably looks strange to someone opening the freezer who doesn’t know what I am up to, but it works. You might be advised to share what you are up to with anyone else who happens to share access to your freezer. I remember one time when I was forcing hyacinth bulbs in the basement freezer and my sister happened to be visiting and opened the freezer only to be completely mystified as to why I was freezing dirt! Just saying…
One other unique aspect of working with Corian pen blanks is that the smell when cutting, drilling or turning these blanks is quite distinct and I would imagine that it could be bothersome over time to some turners. The only thing I can think to do about the odor, if you are determined to use Corian blanks, is to be sure you have adequate ventilation at all times, which is wise regardless of the blank material you are using, especially during the gluing phase. My shop is, unfortunately, in a rather enclosed space, so I use a room fan facing away from the shop to draw away noxious odors out towards the outdoors whenever I am working with any blanks or other ancillary supplies that have unpleasant or potentially dangerous vapors or smells.
Gluing and Milling Corian
Once you have the blanks drilled, the rest of the pen making process is pretty straightforward and identical to using any other material. Corian glues quite easily and while I do continue to rough the brass prior to gluing, I only use medium or even thick cyanoacrylate, commonly abbreviated as CA, (Super Glue is a common trademarked name) for gluing. When using wood blanks I first apply thin CA inside the blank to help stabilize any potential cracks or other imperfections in the wood, but I don’t find that to be necessary with Corian as it is almost always completely uniform throughout the blank.
I do use a drill press for milling the ends of the blanks because I find that the drill press affords greater flexibility in placement of the blanks than is remotely possible using the special chucks on the lathe that I find so useful for the center boring drill process. This use is, in fact, the only reason I maintain the drill press in my shop at this time.
Turning and Finishing Corian
The actual turning of the blanks I find to be exactly like turning wood blanks. I use constantly sharp tools from the Easy Wood Tool line that feature replaceable carbide cutting tips that never need sharpening. Sharp tools will always provide the best possible results regardless of the material and this is certainly true with Corian as well. Dull tools will cut rough, requiring more finish work, or they will simply break the blank completely. It is always worthwhile to sharpen frequently or use replaceable cutting tools. Corian, similar to acrylic in this regard, will have a dulling effect on your tools, so sharpen or replace regularly, especially if you notice even slight decreases in the quality of the cuts you are making that you are sure can’t be attributed to technique alone. Work with the lathe at a reasonable speed, probably not more than 1200 RPM, exercise patience, and you should have excellent results.
I find that well cut Corian blanks require minimal, if any, sanding. I scoff at people who claim these results with wood pen blanks or bowls, but with Corian I think it quite reasonable to start sanding with nothing lower than 220 and even that might be too coarse depending on the quality of your cuts. As with any acrylic or plastic, I sand down through all the micro-fine grades of abrasive as far as 12,000 grit. For the final finish, I use specially designed products, either Hut Ultra Gloss Pen Polish or Craftics 20/20 Plasti-Polish, available from Craft Supply USA and also other specialty retailers. These products provide a final micro abrasive shine and finish intended especially for acrylic blanks and I am always quite pleased with the results.
Where and How to Find Corian Pen Blanks
Corian pen blanks are easy to find, especially on EBay, are usually quite affordable, especially in bulk quantities, and once the process is understood and practiced, are quite easy to work with. Another potential source of material, that might even be free, is to contact a local countertop installer and ask if you can go through the scrap material in search of usable blanks, or cut offs that you can turn into blanks. Many installers are happy to let you reduce some of their waste burden, and while I have heard of some hobbyists who are dedicated “dumpster divers,” and while this practice is usually completely legal, it is usually better form to ask first and never leave a bigger mess than what you found when you got there. Sometimes hobbyists will sweeten the deal by offering the make gift pens for customers that match the recently installed countertops. It never hurts to ask local installers about the options!
I find Corian to be a rewarding material to use as a pen blank because of the amazing variety of colors and designs that are available, unequaled by any other blank material, especially in the mimicry of marble and granite, materials that are not realistic to use in pen making but whose appearance appeal is wide. Any pen maker who is experienced in using, and is pleased in working with, acrylic should have no problems working with Corian, and if you are new to pen making, or just new to using materials other than wood, I think Corian makes an excellent “entry” material to working with non-wood pen blanks as it is far easier than many other acrylic blanks yet distinctly different in some respects from working with wood. Whether you choose to try working with Corian or not, have a good turn today.