Finishing processes
There are two stages to finishing polymer: sanding up gradually through multiple grits of sandpaper to smooth and refine the surface. And buffing / polishing the surface to produce a high glass-like shine.
OK, so you've made something wonderful, carefully put it into the oven, and hopped excitedly from foot to foot while it cures.
Unfortunately, when you take your pieces out of the oven, you may be a little underwhelmed. They may look a bit rough around the edges, They might be bumpy or slightly amateurish-looking. If so, it's likely that they will need a bit more work.
Naturally, polymer has a fairly matte surface. However, part of its appeal is the way it can take on many different appearances. A proper finishing job can produce :
​
-
an amazing deep mirror shine which brings out the colours and makes a piece look amazing.
-
a silky, tactile matt finish which looks expensive and feels almost frictionless as you stroke it.
-
a satin effect - a subtle sheen, like you get on a conker.
​
Unfortunately all of these effects rely on one thing: proper finishing. And that starts with sanding.
There aren’t many people who actively enjoy sanding. It’s laborious and time consuming, and it’s yet another assault on your poor hands.
BUT… if you’ve created something you love and will enjoy wearing or using, it will multiply your pleasure a thousand fold if you finish it properly.
Quick links to:
​
What difference does buffing make? Move your cursor over the pic to see before and after...
Sanding
How to approach sanding depends a bit on where you’re starting from. If your piece is badly misshapen or extremely “textured” it may not be worth trying, especially if you have thin sheets of a patterned veneer over a base clay. This is because you’ll very likely sand through the veneer and into the base clay, before you have managed to shape the piece to your satisfaction.
So the rule is to try to make your piece as close to the way you want it BEFORE it goes in the oven. It’s much easier to get clay to behave while it's still in its uncured state. If you cure it with lumps all over, and bits of scrap clay and dog hair stuck to it, you’re making life hard for yourself.
There are some good ways to cut down on the amount of sanding you’ll have to do before your piece is cured. These include:
-
Deciding in advance that your piece is going to be textured in some way (eg by using texturing tools, or pressing sandpaper sheets into the raw clay to give it a pleasingly 'even' roughness)
-
Using cornflour and a “pounce”to smooth the surface
-
Putting layout paper over your clay and rubbing it smooth with your fingertips (also known as 'burnishing')
-
Spending a lot of time patting and stroking your clay
-
Wearing latex or nitrile gloves to avoid fingerprints and nail gouges.
-
Using fibrefill in the oven tray.
However, in most cases you will still need to sand to get the full professional effect.
How to sand...
A cornflour 'pounce' can help reduce the need for sanding off fingerprints etc.
Various grades of wet-and-dry sandpaper.
-
Big bowl of warm water.
-
Tiny spot of washing up liquid.
-
Wet and dry sandpaper pieces, starting at least 240 and going up to 1000 or 1500.
-
Put your pieces in the water to warm up.
-
Put a towel over your knees and another one under the bowl to catch drips.
-
Plonk yourself down in front of the TV (it takes long enough for you to get very bored if your brain isn’t occupied) and let your hands do the work.
All you need for sanding your polymer - towel, warm water, sandpaper.
Short answer: Experience!
​
Long answer: At first the piece will feel slightly grippy to the sandpaper in your fingers. Then, as you progress with that particular grit, you will start to notice that the sandpaper doesn’t bite into the piece like it did at the beginning. As soon as your sandpaper doesn’t feel like it’s doing anything, change up to the next lowest grit that you have available. (You will notice that the new paper grips again...)
Rule 1: Go up in smallish stages – not from coarse to fine in one go (tempting though it may seem). In my experience, its fine to go from 240 to 600 to 1000, but it’s not fine to go from 400 to 1200. You can go from 240-400-600-1000-1200-1500 for the full high mirror polish effect. By the time you get to 1500, your piece will feel like something created in a NASA laboratory...
Rule 2: Empty the water from your bowl between the lower grits and the higher ones, because suspended grit and particles in the water will gouge your newly perfected finish. It’s OK to do 400 and 600 in the same bowl, but I’d change the water (and therefore get rid of the gritty sediment) beween 600 and 800 or 1000.
For each grit, the aim is to give each section of the piece a good rub in several different directions. Try not to just sand in one direction as you’ll simply deepen the scratches the previous grit made.
Phew, I made it to 1000. What now?
Again, its up to you. If you carry on going higher, your piece will eventually become satiny and feel amazing. If you then buff the piece, you will get the full deep mirror shine. Or you can stop at 1000 and buff and get a slightly less spectacular shine (you probably won't notice the difference, to be honest).
If you have perfectionist tendencies, you can buy a marvellous product called Micromesh for higher grits. It’s more like fabric than sandpaper and it lasts a long time and is nicer to use, but it isn't really sandpaper any more - its more a part of polishing.
Micromesh starts around the 1000 mark and goes up to 12,000 (yes, that’s 12 thousand!) but as yet, I've never needed to go that high.
Powered Sanding....
If you're lucky enough to have a bench grinder or bench polisher, you've got the option of taking out some of the donkey work of sanding.
A while ago I bought a Foredom bench polisher which I love and couldn't live without.
I use it for the coarser level of sanding, using nylon jeweller's finishing wheels that I get from www.polishingjewellery.co.uk.
I also buy 'goblet' and 'cylinder' Silverline sanding wheels from Amazon - they're cheap and you can shape them to fit whatever you're sanding.
How do I know when to move up to the next grit?
-
I use the wet and dry sandpaper that Halfords (in the UK) sells for car body repairs. Last time I looked, they sold a handy mixed pack of different grits for about £6, which would do very well as a starting point.
-
Usually the lower (coarser) grits like 240 and 400 take the longest and are the hardest work. They will remove relatively large amounts of clay and you can - carefully - remove lumps and humps and sharp edges with this grade of sandpaper, as long as you are careful not to sand too deep into your piece.
-
As you work on these lower grits, remind yourself that you’re doing most of the legwork here, so that when you get up to higher grits you’ll only need a few seconds or a minute or two on each piece.
-
At the higher grits (800+), you’re simply refining texture rather than fundamentally changing the shape of the clay.
-
What you're aiming for: A piece that feels consistent to the touch – and it will be touch rather than sight that you use in this process. (It sounds weird, but if you put the piece to your lips, you can tell whether it needs more).
What sort of sandpaper do I need?
One of the great things about polymer is that it will take a really spectacular shine if you sand it thoroughly, and then buff / polish it.
If you haven't already sanded your piece, DON'T try buffing, as you'll just draw attention to the imperfect surface (unless that's the effect you're going for!).
SO, if you've still got sanding to do, go back to the info on sanding right now!
If you're ready to buff your piece, your options depend on what equipment you've got to hand.
Buffing / polishing
If you're anything like me (and most other creative / crafty / handmade people I know) you will probably already have access to some basic power tools, which will make buffing your polymer pieces a lot faster and more effective.
Probably the most ubiquitous of these (at least in the UK) is the rotary power tool or Dremel.
These are basically high speed drills which spin a tool at the end of the shaft. The problem with them is that they're small and furious, and come with a load of tools and accessories, none of which are much use with polymer.
Don't attempt to buff or even sand your pieces with the Dremel accessories - no, not even the harmless-sounding 'felt' wheels. They're designed for metal and wood and are far too harsh (unless you actually want to gouge out huge chunks and strip the design off whatever you've made!).
Basic Buffing
What material should I use for buffing?
The best material I've found for polishing polymer clay is polyester felt. This comes in cheap sheets in loads of colours in places like Hobbycraft (it's in the kids craft section). I tend to buy the white sheets, just in case there's any colour transfer.
You make your own buffing wheels. Don't freak out - this sounds harder than it is! Using a marker, draw half a dozen 2 inch circles on your felt, cut them out with scissors, and snip a tiny hole / slot in the very centre of each circle (just big enough to shove the end of the mandrel through).
Make a sort of layer cake with the circles, and then pierce through the middle with one of the Dremel's accessories - it's mandrel 402, which has a screw on top for holding things in place. Put the screw back on top and tighten.
If you then mount that mandrel on your Dremel, you will find that a medium speed and a light touch gives you a very beautiful high polish in fairly short order.
In fact, I still use my Dremel to polish the insides of bangles, because my bench polisher is too big.
A word of warning - very high speeds make this small polyester buffing wheel quite harsh, so you need to go easy, otherwise you'll end up overheating the clay and you'll get nasty streak marks instead of the beautiful shine you were aiming for.
If you get the streaks, you'll need to do a bit more sanding with a fine grit to restore the surface, before re-buffing (but a bit more carefully this time!).
​
​
So how do I use it?
A bench grinder or high speed tool can really help with buffing...
​
The wheel here on my Foredom is a largish cotton mop which - gently used - can give you a really high shine on well-sanded polymer.
This is my Dremel with a home-made polyester felt buffing wheel. Great for the inside of bangles and anything else you can comfortably hold with one hand while buffing with the other.
These are the sheets of cheap white polyester felt I buy from Hoobycraft to cut up to make my own buffing wheels.
I've discovered that a really soft jewellers mop - like this Swansdown one - will also work brilliantly on well sanded polymer. Only really works with a bench polisher tho - far too big for a hand-held tool.
Buffing / polishing with power tools
If you've done a good job with the sandpaper and have reached at least 1000 grit, your piece will respond very positively to a vigorous rub all over with a piece of soft cotton cloth (eg, an old pair of jeans).
This 'elbow grease' sheen is actually very attractive - not as glassy as the full-on polish - but subtle and classy and nice to the touch.
If you want a really high shine without power tools, you'll need to go as high as possible with the sandpaper before tackling the buffing stage...