Sanding and polishing polymer clay produces a glassy appearance, which can be very beautiful. The look you are trying to achieve will determine the extent to which you sand, and whether you buff or add an acrylic gloss, or both.
Sanding is not necessary for a finished look to polymer clay. The clay has a slight texture and matte appearance in its natural state after baking. This can often be the desired result and requires no further attention to the surface. Or perhaps a texture is desired, but with a gloss finish to it, so sanding techniques would not be necessary.
However, for the smoothest, glass-like shine, the process of sanding and polishing is best. Sanding by hand produces the highest quality smoothness and shine, but sanding can be accomplished by using a rock tumbler, thus taking less time to sand multiple pieces. Desiree McCrory has an excellent tutorial for tumble-sanding and tumble-polishing polymer clay, HERE.
The sanding process is done wet, so that the sandpaper is used most effectively and the dust from sanding doesn’t float into the air. 3-M WETORDRY sandpaper is most commonly used, and is available at your local Wal-Mart, in the automotive detailing area. I highly recommend getting grits 220, 320, 400, 600, 800, 1000, 1500, and 2000. The 220- 600 grits come in a large combination package of 8.5″ x 11″ sheets. The combo pack is labeled “fine”, “extra fine”, etc, but if you look on the back of the package, you will see a grit associated with each label. These grits can also be purchased individually in packs of 5 sheets. The other grits, 800-2000, are only sold individually and come in 3.75″ x 9″ sheets, in packages of 5 sheets each.
You can invest approximately $20 in sandpaper at Wal-Mart, and it will last you a LONG time, because the sandpaper is reusable. For sanding by hand, cut the sheets into smaller pieces, approximately 3″ square, and write the grit number on the back of the sheet with permanent marker. After sanding, simply rinse well and allow to dry. Store the sheets in a zipper sandwich bag for later use. These sandpapers can be used an average of 4 to 6 times before they lose their effectiveness, but they are the most effective the first and second times.
Also available are 3M Micron Polishing papers, in grits 400 to 8000. I purchase these papers from Santa Fe Jewelers Supply, and they are an excellent product for professional finishes on polymer clay pieces. I usually purchase only the 4000 – 8000 grits.
It isn’t necessary to begin sanding each project with the roughest grit you have. To determine the grit of sandpaper needed, you would run a finger over the surface of the clay being sanded, and choose the grit that most closely resembles the texture. If there are sharp areas or raised bumps, a rougher grit wil be necessary in those areas.
Sanding Canework: depending on the thickness of the slices used, it is best to err on the side of caution when sanding caned items. Thicker slices can take more sanding, so a lower grit can be used. However, if the slices used were quite thin, then be vigilant in watching the item as you sand, rinsing often, and checking the item for areas worn thin by sanding. If areas are thinned to the point that the canework becomes translucent or is sanded off completely, then avoid sanding that area with consecutive grits.
THE SANDING PROCESS
This can be a little bit messy, so I recommend you use a couple of paper towels or a towel over your work surface or lap, to catch drips.
- Fill a large bowl half-way with warm water. Add a few drops of liquid dishwashing soap or Jet-Dry. This will cut the surface tension of the clay and make your sandpaper last longer.
- Wet the sandpaper and hold it above the bowl. Wet the baked clay item you are sanding. Rub the sandpaper lightly over the clay. Use back-and-forth and circular motions, for 30 seconds or so, rinsing both the clay and the sandpaper often. The sandpaper will develop a whitish sludge as you sand, and this is normal. If your water becomes cloudy from the sanding sludge, pour the water down the drain, rinse the bowl, and re-fill with warm water and dish liquid.
- Repeat with each consecutively higher grit until clay is as smooth as desired. Wash the clay with soap and water to remove any residue from the sanding. Rinse well and dry with a lint free cloth.
Rinse the sandpaper pieces, and set aside to dry. Store in a zipper baggie.
BUFFING
Polymer clay can be buffed to a high natural gloss after sanding. The faster the buffing material is used, the higher the shine will be on the clay. By hand, a piece of old denim will give a satiny finish – try rubbing the clay back-and-forth across the leg of a pair of well-worn jeans (new jeans will cause some of the dye to rub off on the clay, giving it a blue or black cast, depending on the color of the denim).
Using a rotary tool, such as a Dremel, with a polyester felt or denim rotary wheel, will bring the sanded clay to a high gloss. (Note: Muslin wheels that come with rotary tools are usually not the best to use, as the muslin can scratch the sanded clay.)
You can purchase polyester felt at WalMart in the craft section, and create your own buffing wheel by following the instructions on Desiree McCrory’s website (which is full of excellent tutorials, by the way). You can find the instructions for creating a buffing wheel HERE.
POLISHING
Polishing and buffing both bring out truer color in the clay, making clay items more vibrant. Polishing can be done in addition to buffing, for a super-glossy surface that when completely smooth, is visually indistinguishable from glass; yet unlike glass, polymer clay is lightweight even when quite large, and extremely durable.
There are a number of different ways to polish your clay. Simply giving it a few coats of a water-based acrylic, such as Rustoleum Verathane (my preferred brand), will leave a lasting and protective glassy shine on your clay. It is a good idea to use a polish that won’t yellow over time. Check the label of the waterbased polish you choose, to see if it says whether or not it is non-yellowing.
Note: With the exception of the Rustoleum Varathane waterbased spray, aerosol based, spray-on polishes or oil-based polishes will adversely affect the clay and end up causing it to become permanently sticky and/or cloudy. Nail polish is also to be avoided for this reason, and will result in similar negative effects. However, If there is a buffer layer between the clay and the oil-based polish, such as a waterbased sealer, then it is okay to use an oil-based product on top of that.
Usually it is best to use a little bit of the brush-on polish in a smaller, separate container from the main can or bottle, to prevent contamination (dust, hairs, bits of sanding sludge, old dried polish). Use a container that has a good, tight seal. Pour a small portion of the polish from the main container into the smaller container, and wipe up any drips with a damp paper towel. Tightly seal the original container and work from the smaller one until either the polish becomes contaminated or gets thick.
The polish can be dipped in or brushed on. For dipping, the polish must be thin enough to allow for adequate dripping without causing streaks. The polish should be no thicker than the consistency of milk. A large enough container and enough polish to cover the item are necessary. For small pieces, such as beads or brooches, a disposable plastic cup could be used. If there is a place from which the item will hang, such as a loop, hook the end of a piece of wire, about 10 inches long, around that. If the item has a hole, make a loop at one end of the wire, and slide a seed bead onto the wire and slide it down to the loop as a stopper bead. This prevents the clay from sticking to the loop and causing them to bond together when the polish dries. (If the clay item has larger holes, a larger stopper bead may be necessary.) Alternately, a wooden skewer or toothpick can be pushed into the hole of the item, firm enough to hold without dropping, but not firm enough to crack the hole. If the item has no holes, you could lay the item onto a wire rack with a few paper towels folded underneath it to catch drips, and pour the polish over the top. This method does result in some waste of polish, however.
For dipping, lower the item into the polish until it is completely covered. Lift the item out and allow the polish to drip off until the dripping stops and a ’bead’ of polish forms at the bottom of the item. Use a torn edge of a paper towel to touch the wide bulb of polish at the drip, and gently draw the paper towel down and away from the clay item. The ‘bead’ of polish will come with it. It may be necessary to repeat this process every few minutes until all drips have been pulled away from the item. Hook the top end of the wire and hang over a cabinet doorknob, curtain rod, or other suitable suspension so that the polished item does not come in contact with any other surfaces until it is dry.
For brushing, I prefer an artists’ Kolinsky sable brush, but they can be expensive. Sable hair brushes of medium quality are fine, though; just check the brush for loose hairs, dust, or debris before polishing your clay. Dip the brush in the polish until a ‘bead’ (drip) of polish appears on the brush. Never dip the brush all the way down to the ferrule (the metal base of the hairs). Only dip the brush approximately halfway. Don’t wipe the brush on the edge of the container – this allows polish to dry on the inside wall of the container and could dislodge at a later time, contaminating the polish. If you need to, you can wipe the edge of the brush on a clean paper towel. Pick up your piece and hold it at a 45 degree angle. Use the drip at the tip of the brush, and touch the ‘bead’ of polish to the top or edge of the surface of the clay. Work the ‘bead’ of polish back and forth across the clay, until the ‘bead’ is nearly gone. Dip the brush into the polish again, and touch the ‘bead’ of polish on the brush to the nearly gone ‘bead’ of polish on the clay. Work quickly, so that the polish on the clay doesn’t have a chance to dry and leave streaks when re-dipping the brush. Keep a cup of warm water nearby and rinse the brush frequently – this will prevent polish from drying on the hairs and ruining the brush.
When the surface of the clay has been covered, then set the item aside to dry. Prick any bubbles with a needle. Depending on the temperature, humidity, and thickness of the polish, drying can take as little as 10 minutes. When in doubt, allow the polish to dry overnight. To heat-cure the polish and permanently adhere it to the clay, bake the clay item again, at 200 degrees, for 10 minutes. Repeat this process for the desired number of layers of polish.
After a polishing session is finished, wash the brush with a good quality shampoo and conditioner. This will keep the brush in optimum care and will remove any residues of polish on the brush. A high quality brush will last much longer this way and be worth the investment.
