TOOLS Sanding polymer clay basics

There are several options to finish the surface polymer clay objects after baking. You can:

  • do nothing. honest.
  • coat/seal the surface with an acrylic liquid (Future, Golden, Varathane are some popular liquid brands)
  • sand
  • sand then coat/seal
  • sand then buff with a wheel of fabric like very soft cotton or acrylic polyester to create a glossy or semi-glossy finish

Which finish should I use?
It's strictly a personal preference and dependent on what's going on on the surface. If you've done a nice smoothing job prior to baking, you may not have to do anything after baking to finish the surface. If the surface has a dusting of Pearlex that you want to protect or a thin layer of paint, sanding wouldn't be a good choice.

Why bother sanding?
A nicely sanded polymer clay surface is not at all shiny but feels absolutely wonderful. And the combination of sanding and buffing produces a nice shiny finish. Because of the more intimate surface feel, sanding/buffing finishes are wonderful for polymer clay jewelry.

 

Sanding pluses

Polymer clay takes on great seductive feel when it's been well sanded. Over time it also takes on a soft semi-glossy final luster, if it's rubbed and worn against fabric (e.g. beads on a necklace).

The finish of a good hand sanding is still the ideal. If you choose to hand sand, save that task for your most precious items. The next best thing to hand sanding is using power tools. Powered sanders, brushes and rock tumblers can do the hard work and save your hands, wrists, etc.


Sanding minuses

Sanding can be a demanding task. It's really not worth doing at all, if you don't plan to do it right.

Few like hand sanding for more than a few minutes. It can be tedious and painful. It's been known to try one's patience and aggravate tendons, ligaments and muscles. It can also be challenging to find the right media and the right progression of that media. Wet/dry sandpapers and sponges are the hand tools of choice for polymer clay, since you need to sand polymer clay while it's wet to trap sanding dust.

If you prefer to save your hands and sanity, etc., get a powered tool. Rotary/vibrating sanders and rock tumblers cost but not as much as the trying to repair any damage to you caused by improper or prolonged hand sanding.


Buffing pluses

A great next step after sanding polymer clay to produce a wonderful shine. With few exceptions, buffing is completely dependent on having a well sanded surface. When producing fauxes, like turquoise, jade, ivory, amber, etc. buffing produces a wonderful and realistic finish that a coated finish cannot touch. The surface can be shiny, but recesses, nooks and crannies can remain matte; producing a realistic appearance. A sanded and buffed surface is easy to restore because it’s not protected by a coating.

You can produce a semi-gloss shine by just rubbing on a soft cloth like your jeans.

Click here to learn more about buffing options.


Buffing minuses

Yet another finishing step and always requires a power tool for a really shiny effect. Buffing won't work too well if the surface isn't smooth enough. A high gloss buff requires a high rpm power tool, special wheels for polymer clay, a light touch which requires practice and focus (to avoid injury).


Coating, varnishing pluses

A different great step after sanding. With the right material and application method, coating does a great job for finishing and can protect the clay’s surface from excessive wear, dirt or moisture. There are several finishing options like there are in paints; matte, semi gloss and gloss. Once applied, the finish tends to hold that finish for a very long time, unlike a sanded/buffed surface.


Coating, varnishing minuses

If not applied under the right circumstances, can make the coated piece look “plastic-y” and cheap. And you need to make sure to avoid creating bubbles. Unlike a sanded/buffed surface, it can more involved to repair/restore a damaged coated surface.

 

  Sanding tools
Manual labor
  a well conditioned pair of... um, hands   sandpapers, micron papers, polishing papers, finising sheets sanding sponges

Battery powered appliances
  modified battery powered toothbrush battery powered cleaning brushes (e.g. scumbuster, stain brush)  

High powered tools
  oscillating sanders (e.g. Mouse) a rotary rock tumbler a vibrating tumbler

 

  Basic Wet/Dry Sanding Sheet Sets
standard or grade values
CAMI or C 200s, 300s, 400, 600, 1000, ...
FEPA or P 200, 400, 800, 1200, 2000, ...
micron 400 (30m), 600 (15m), 1200 (9m), 4000, (3m), ...
sponges medium, fine, super fine, ultra fine, micro fine

Where do I get these sets?
Wet/dry sandpapers and sanding sponges can be found in many places. The most common are hardware, woodworking, automotive repair and plastic supply stores. The progression selection is, however, hit and miss. If you live in a metro area and want the best range of grits, seek out an automotive paint and body supplier. Those are the businesses that sell supplies to auto body repair shops so they have a comprehensive variety of wet/dry sandpapers. But they may not sell individual sheets because they are a business to business supplier. Reputable online suppliers are another great option.

The coarser grits (lower numbers) are for grinding purposes - quick removal of lots of material, removing defects, shaping a piece that's not quite right. The higher the number, the finer the paper. The goal is to make all of the scratches left by the previous sandings finer and finer so they won't be visible, especially after buffing or after a coating is applied. When sanding, start with the lowest grit you can get away with, then step up higher. Up to 600C, it's best not to skip the grit values in your set, otherwise you may not remove the scratches from the previous grit.

It's easier for you if all your papers come from the same manufacturer and they're the same standard or grade (CAMI, FEPA, or micron). If you've got papers from different manufacturers, and/or have a mix of standards, use this equivalent table to keep your progression on track. For example, a 450C = 800P.

Wet/dry silicon carbide paper is dark gray on the front. The standard and grit value is usually printed on the back. Amazingly, some papers do not have the standard printed on them at all. If you know the standard, write that on the back. It's a pretty good assumption that 3M papers, like the ones in the hardware stores, are CAMI. 3M does make FEPA papers, but they will be marked with a "P". If you don't know the standard nor the manufacturer, toss those sheets. They're not worth anything if you can't fully identify the paper's ability.

Online Industrial Supply.com is a good online source for the FEPA bulk sandpaper purchase.

Judge by outcome
After 600C, judge by outcome. If you've been sanding well through to 600C, then jump to1500C and don't get a perfectly smooth glassy shine after buffing, try using the 1000C then 1500C. Another thing to judge by outcome - if you can see any scratches after buffing, your sanding efforts didn't quite pay off. Somewhere along the way you either missed a spot, or some of the coarser grit broke loose from the paper and stayed in sanding water and ended up trapped between the paper and the clay surface.

When should I stop sanding?
What's the final grit? When should you stop? That depends entirely on you. If you plan to buff and want the shiniest gloss, get well into the higher end. With a bit of practice and time, you'll find the stopping points that's right for you and your specific application. The silicon carbide papers and sponges don't go as high as the micron papers. Although you can go much higher with those micron sheets, some question whether it makes enough of a difference for a polymer clay surface.

Note:
You may have noticed, I only addressed coated media, not loose media like the loose grit used for tumbling rocks, sand, walnut shells, corn cobs, etc. Some have used loose grit and sand with success. Those materials have not been my preference, to date, for various reasons. Generally, I prefer the abrasive particles to be stuck to something. I don't care for loosey goosey media.  :)


  Hand sanding  

Gather your things and get comfy. You will need:

  • polymer clay pieces to be sanded
  • medium sized bucket or pan for holding water
  • comfortably sized sheets or sponges (sanding media)
  • soapy or silky water (add detergent, bath foam, etc.)

The goal is to make all of the scratches left by the previous sandings finer and finer so they won't be visible after buffing or after a coating is applied.

Comfy? Begin.

 
  1. sandpapers usually come in 9"x11" sheets, generally too big to hold in your hand or for sanding small objects, so cut or tear them down to size. Make sure you write the grit values on the back with a permanent marker because whatever is already printed on the back might not show on a smaller piece.
  2. soak the papers until they get a little less stiff, set aside all the sanding media except the one you need at the time. start with the coarsest media.
  3. toss in your polymer clay pieces into the water.
  4. sand in a circular motion as much as possible, use gentle pressure. rinse the media and your piece when you notice the scraped material (debris) clogging your media. the soap helps reduce clogging.
  5. after sanding each piece on all appropriate surfaces/sides, set that piece aside (outside of the pan). this will help you keep track of what needs to be sanded and what has been sanded. one way to tell if you've sanded the entire surface is to apply a acrylic paint wash to the surface and let it dry. if you don't see any paint on the surface after sanding, you've done a good job.
  6. when you've finished that round, rinse your sanded pieces, empty the pan and refill with fresh soapy water. this will help prevent any coarser grits getting into the finer sanding levels.
  7. repeat steps 3-6 with the next finer grit.
  8. when you're done sanding, rinse your pieces well in clean water then wipe them well with a soft cloth.
 

Note 1: Ergonomics
It is possible to hand sand without causing damage or pain to yourself. I can't recommend any specific positions or devices, but I would recommend if you experience any pain or discomfort while sanding, take a break. Then change things around; the positions of your hands, arms, wrists, change your sanding height level. Relax your shoulders. Take your time. Take frequent breaks. You may eventually discover the magic formula of how to position yourself and amount of sanding pressure for a tolerable or even pleasant sanding experience. If you do, let folks know! ;-)

Note 2: Papers vs sponges
Papers are fine for nearly every situation. Sanding sponges for better suited for contoured surfaces because they will follow the uneven surfaces better. If you can't find sanding sponges, you can wrap a sheet of sandpaper around a regular kitchen sponge.

Note 3: Post-sanding white residue
Sometimes after sanding, the might be some white residue on your pieces after they've dried. If rinsing and wiping didn't prevent that from appearing, try rebaking for 10-15 minutes, or zap with a heat gun.


  Sanding small objects with a battery-powered appliances

OK. Me and battery powered tools aren't the best of friends. I only use them when I have no better choice, like for a cell phone, etc. But at home, gimme A/C current. I don't have to worry about recharging and keeping track of various power pack supplies.

So I can't really address modified electric toothbrushes, stain brushes, etc. because I've not used them.

Eva (Mejsel) of Denmark has. She modified an electric toothbrush. Her efforts are highly worthy of mention. She posted the info at polymerclaycentral.com's message board in this message.

These little appliances seem ideal for sanding small objects and getting into small spaces. Since electric toothbrushes, stain brushes and the like a pretty common and inexpensive these days, it seems a nice choice.

The toothbrush, your sandpaper set, a little glue and you're good to go,


  Sanding with a Black & Decker Mouse  

I've already done a separate tute for that specific task. Click here. I must confess, I don't use my Mouse for wet sanding unless I'm doing production level work, which I avoid these days.

Why just for production level work? Two small reasons. One, the vibrating hand held device that has a wet sanding surface can get a little messy if one doesn't have the proper setup to contain the spray. Two, the sandpaper must be velcro-ed to the Mouse. It can be hard to pull those sheets off to change them when you've got tendonitis, etc. If I had a mouse for each grit, then sweet. Otherwise, not so sweet.


  Sanding with a Tumbler  

I've done a separate tute for that as well. Click here for a tute on using river rocks in a tumbler to sand polymer clay. Unless I've literally only 1-2 beads, I will use my tumblers and rocks to sand.

You've a tumbler and sandpaper, but no river rocks? Click here for a tute on how I used sandpaper to tumble sand polymer clay.



There's nothing better than having a great tool when you need it.

Enjoy,
Desiree

Last update to this page: 10 Mar 09. Send comments, questions or suggestions to Desiree McCrorey.