Materials Everything I know about FIMO (and Sculpey, and Cernit...)

Thought it would be nice to add my 2 cents to the wealth of information here. Please feel free to correct me, and add more!

What is Fimo?
Fimo is a polymer clay developed in Germany in the 1930's and marketed world wide by the Steadtler company. These are not clays in the classic sense of the word, but a mixture of polyvinyl chloride (also known as PVC or vinyl) and a "plasticizer". When put in the oven the plasticizer evaporates, and the rest of the material polymerizes in a solid slightly flexible plastic. Sculpey is a differend brand with a very similar product, and has a bigger market share in the US.

Health effects.
PVC is not something you want to burn, as vapors of burning PVC contain chlorine and dioxins. But, you will have to overheat the oven quite a bit for that to happen. Always use breathing protection while sanding. There is some concern about the plasticizers used in some of these materials; I have been able to find very little information about what is actually used. FIMO Kids is a CE-certified product that is marketed as safe to use by children. It is probably not safe to eat.

Working with FIMO.

Fimo now comes in several types and is packaged to appeal to several different markets. The main types are:

FIMO Classic: the original, this is a rather firm clay that needs quite a bit of kneading before use.
FIMO Professional: not sure what the difference is, comes in larger blocks. This comes in a range of skin tones designed for dolls.
FIMO Soft: this is the more pliable version, and what I prefer to use for doll heads.
FIMO Kids: this is even more pliable and soft, and marketed towards children.
FIMO Effect:various effects, like nightglow, glitter, translucent, metallic, stone, pastel, gemstone.
FIMO Liquid: this is not a clay at all, but a thick gel that bakes into a transparent layer. Nice for jewellery.
FIMO Air: This is not a polymer clay, but an air-drying lightweight clay. Do not mix with the rest!


Before you begin
-When I have an existing body to work with I take a part of it with me to the shop to find the best possible match. Keep in mind that lighting in stores is not always good, and it is best to compare colors in daylight or several different light sources if possible.

-If a good match can not be found, the right color will have to be blended. This is quite annoying work, and tricky to get right. It is best to start with a small amount to get a rough idea of the amounts of each color needed. Keep in mind that the darker colors have a lot of pigment, and a little goes a long way. Some skin tones have more yellow, some more pink, and recently I had one that needed almost a whole block of very light grey. FIMO sell a set with a range of colors and a mixing chart to help with this and what a thing of beauty it is.


-I usually weigh one of my previous heads and then mix quite a bit more than the weight of it to make sure I don't run out of clay halfway trough! Especially important if it is a custom mixed color!

-I have mixed FIMO with Sculpey without any problems, but when in doubt, do a baking test with a small amount first.

-FIMO can be quite firm to work with, especially if it has been on the shelf for a while. Some of the darker colors can be hard and even crumbly. A good knead with warm hands usually solves the problem. If your clay is really uncooperative, try mixing it with "Mix Quick", a medium designed to soften older clay.

-For mixing FIMO, I roll it between my hands into a long thin roll, twist it, roll it into a snail shell, roll it into a long thin roll, twist it, roll it into a snail shell, roll it into a long thin roll, twist it,etc etc etc until I have a nice even color. Cut trough the clay roll a few times and look at the cross section to make sure that you have an even mix.

-Before I begin work I make sure that my workspace and hands are as clean as I can get them. I clean my desk and tools and put a new sheet of paper on it as an underground. Especially light colored FIMO attracts every bit of dust in the room and the dead skin cells on your hands and can get really grey, grimy and nasty. And there really isn't so much you can do about it, apart from working in a quick and determined manner. I keep a scalpel at hand to scrape off hairs and other bits of dirt that attach themselves to my project.

-Also, I remove nail polish as I have found it sometimes reacts with the material.

-As for tools, this isn't really the place to go into that, but a simple bamboo satay stick has always been my best friend, and a clean and easy to replace one of that.

-if you are using a core to sculpt around, keep in mind that unbaked FIMO reacts with polystyrene. Polyethylene Ziploc bags work fine for storage, but I once stored some FIMO in a polystyrene box and it just melted. If you use a polystyrene foam core wrap it in tape to keep it from becoming a nasty sticky mess. Also, during the bake, the polystyrene will shrink and gasses will try to escape. I leave a few small holes in my heads (I use a thin stick or needle to pierce the nose holes, the holes of the ears and also I usually poke a hole in the back of the skull) to keep the head from cracking because of gasses building up inside .

-When I have very thin bits, like ears, I sometimes give them a little scaffold in the form of a small bead of clay underneath to prevent them from collapsing in the oven. The scaffold is removed with a bit of cutting and sanding after the bake. Temporary scaffolds may also be used to keep the object from falling over in the oven.

Good. Now let's get started!
-Well this bit is up to you!

Baking FIMO

-This the tricky bit. I would definitely recommend investing in an oven thermometer, as household ovens are usually way off. The one I have here claims to be at 140 C, when it is actually at 120 C.

-The temperatures listed by manufacturers for different products vary a bit, usually somewhere between 110 and 130 Celsius (230-266 degrees Fahrenheit). The 120 my oven gives me seems to work well for everything.

-Overheating is not recommended. Lighter colors tend to yellow, an unattractive cloudy kind of transparency can develop, and in extreme cases the whole thing just blackens and burns. Should that happen, your project is borked. Switch off the oven, air the kitchen and start again!

-When there is not enough heat the object turns out kind of brittle and vulnerable. Don't worry if this happens, just bake it again at a slightly higher temperature.

-Baking time of 30 minutes is usually about right. If your object is very thick and heavy it may turn out that it is not fully done on the inside. Again, no biggie, just bake it half an hour more on the same temperature as the first bake.

After the Bake

-When the object is hot out of the oven, it is soft and rubbery. If you can stand the heat, now is the time to remove scaffolds, cut off the back of the head, etc. Be careful though, it is still quite vulnerable.
As the object cools down, which can take a surprisingly long time, a chemical reaction takes place that turns it into hard matter.

-only when the object is fully cooled, check if it is properly baked.

-And now you can refine and sand. I have found that sanding pads and blocks made for the false nail industry work well on FIMO- and come in varying amounts of grittiness for a good price. If you have a shop nearby that caters to manicurists it is worth checking out.

-it is possible to add more material to a baked object and bake it again. I must admit that I have only started doing this recently, but so far very good. The new material does not separate from the old, and if you are careful about blending the seams it should be ok.

-FIMO is no full replacement for resin. It does not have the same structural integrity- if your object is going to take a lot of force, you may have to reenforce it. The good news is that you can do this, because FIMO does not shrink.
Also, I think, you will never get that perfectly smooth resin finish. I don't mind that so much, a hand made object looking handmade is fine with me.

-I have used two types of coating on FIMO. Citadel Purity Seal turned out extremely shiny, and I would not recommend it. Mister Super Clear works all right, does not give a fully matte finish, and gets shinier as more layers are added. On top of that, you can do a faceup as you would do on a resin head.

-faceups can be removed with acetone free nail polish remover. Careful though, as it makes the material a bit softer temporarily.


...And I think that's it. If I think of some more I will add it later!

 

Yes, I use files and sanding blocks designed for fingernails as well. They are pretty cheap, and they seem designed for sanding a material that has some flexibility to it.