Here is a little summary of the materials I use most - how they are used and what to keep in mind when using them. Please be aware that my safety advices may not be comprehensive and always read the label and comply with the MSDS that come with your materials. Don’t know what a MSDS is? Then don’t tamper with these materials!
Solids:
polyesther resin:
good allround resin, very versatile. Thickened best with CabOSil (fumed silica), dissolved with Acetone (not thinned!), takes many many fillers such as ground bronze for great fake bronzes. Normally comes preaccelerated (blue colour) and needs MEKP hardener, normally around 4% but amount can be varied in accordance to humidity, temperature and thickness. Tends to burn in curing. Pretty brittle. Very smelly- contains Styrene. Problematic with some materials (dissolves polystyrene, addition cure siliconne will not cure against polyesther resin unless thoroughly tempered)
Cheap though! Reinforced with glass fibres.
Long sleeved clothes, Latex/Vinyl gloves, respirators, goggles recommended (especially for handling the hardener – very corrosive and very runny), ventilation!
Epoxy resin:
Much nicer texture, needs some „fast“ and some „slow“ hardener, normally 20% by weight. Less brittle than Polyesther resin, also gives off toxic fumes, but does not smell as much (but let this not fool you!) Generally similar to polyesther, but more durable. Fast hardener tends to burn. Does not cause cure inhibition with addition cure rubber! Does not dissolve polystyrene! Does not pump styrene into your cast. Reinforced with glass fibres, thickened with CabOSil, aluminium hydroxide or glass balloons
More expensive than polyesther
Long sleeved clothes, latex/vinyl gloves, respirators, goggles recommended, ventilation!
Fast Cast resin:
Two part PU based resin, normally 1:1, cures in up to 5 minutes, comes in a great range (in terms of curing time, hard- / brittleness, and runnyness. Normally very runny which makes it a great casting material for intricate pieces. Can be poured or swivelled, thickened fast cast resins make a great resin jacket for moulds. Fine with addition cure silicones, not smelly, does give off toxic fumes. Bonds to addition cure silicone if the two are combined while curing. Thickened best with glass balloons
Long sleeved clothes, latex/vinyl gloves, respirator, goggles recommended, ventilation!
„Biscuit Foam“ - rigid polyurethane foam
Two part PU foam, comes in various expansion rates – the lower the expansion the harder and heavier the foam. The very hard stuff makes a great quick jacket for rubber moulds, the lighter stuff is very useful for reinforcing from within (say you have cast a head in a thin layer of fast cast that would otherwise easily break – foam it and it will be light and durable!)
Long sleeved clothes, latex/vinyl gloves, respirator, goggles recommended, ventilation!
plaster:
I am sure you all know plaster, but: Did you know you get different grades of plaster? Softest is called modelmaking or superfine plaster, then you get dental grade plaster that gets extremely hard (my favourite is called Crystical R) For our uses, I strongly recommend using the hardest one you want to afford, the harder the plaster the thinner you can make your mould – something that you really need to consider with the heavy plaster. Pretty much stick to the recommended mix ratio of plaster/water. Reinforced with burlap (jute fibre) (moisten before adding)
still a great moulding material, non toxic, easy to use, more surface detail than one might at first think. Brittle of course, heavy as f*. Addition cure silicone does NOT cure against plaster, unless waxed to hell and back or sealed.
Dust mask if you are creating a lot of dust, latex/vinyl gloves if you want.
Flexibles:
silicone, condensation cure /tin cure:
two part silicone, normally 10:1, various curing times, great range of hardnesses, cures against almost everything. Shrinks a little, rips easily after about two years, breathes off alcohol. Not suitable for clear casting materials and delicate PUs and addition cure silicones. Not safe to use on skin. No fumes, if degassed and newly cured it is almost indestructable. Bonds very well to itself if clean. Pretty indestructable, uncured silicone can be washed out with white spirit
Long sleeved clothes recommended, latex/vinyl gloves
silicone, addition cure/ platinum cure:
two part silicone, normally 1:1, various curing times, great range of hardnesses, most durable and accurate rubber. Safe to use on skin, does not cure against moist materials or such containing sulphur (clay, plaster, latex) or styrene or some PU-rubbbers or superglue or actually a lot – its a great great material and one of the safest of the above, but please be aware that it is easy to make it not cure correctly and that can be very very frustrating since it is expensive and not just will you have to start all over again, but you may also have to clean up any residual uncured silicone before your second attempt, or it will ‘infect’ your new rubber. Love it very much, it is your friend, but pay attention to your friends needs, or it will turn against you.
Do wear vinyl gloves NO LATEX – the uncured stuff is pretty tacky
Polyurethane rubbers:
from as rubbery as some silicones to „tupperware“-hard, PUs have the greatest range of hardnesses. Two part rubber, various mixing rates, gives off pretty evil fumes, should be degassed, does not like moisture or oxygen when uncured, super easy colouration with alcohol based inks (Copic, Letraset, Tria) best to keep warm after demoulding for post curing and reducing fumes until not smelly… Decomposes quickly, most not very UV-stable.
Long sleeved clothes (very, very sticky), latex or vinyl gloves, respirators, ventilation, goggles recommended
cushion foam – flexible polyurethane foam
two part PU based foam, various mixing rates, different expansion rates – high expansion: Soft and light, low expansion: hard and heavy. Same as rigid foams. Especially the softer ones need vicious beating after they have fully cured to break the cell structure and make them keep their shape. Sometimes the soft foam collapses like a misbehaving cake without any obvious reason. Make sure you stick to the correct mix ratio (you will need super-accurate scales) and mix it very well, even though it may start to rise really fast.
Long sleeved clothes (very, very sticky), latex or vinyl gloves, respirators, ventilation, goggles recommended
