Materials
We keep four mold compounds and three casting resins in stock. That is deliberately a short list: a material we run every week is a material whose behaviour on a Thursday afternoon in August we can actually predict.
The choice between tin-cure and platinum-cure is not about quality, it is about what your master is made of and how long you want the block to live. Tin-cure is tolerant of contaminated masters and cheaper; it also shrinks slightly over its life and gives up sooner. Platinum-cure holds dimension for the life of the block and is ruined instantly by sulphur clay, latex or tin residue.
| Compound | Shore A | Pot life | Demold | Where it goes |
|---|---|---|---|---|
| Tin-cure, general | 25 | 45 min | 16 h | Bases, simple block molds, masters of unknown history |
| Tin-cure, soft | 15 | 40 min | 18 h | Deep undercuts where the skin has to stretch off |
| Platinum-cure, standard | 30 | 30 min | 6 h | Production kit blocks, anything dimension-critical |
| Platinum-cure, high-tear | 35 | 25 min | 8 h | Fine detail on high pull-count blocks |
Platinum-cure silicone will refuse to cure against sulphur-bearing clays, some latex, some tapes and anything a tin-cure compound has touched. The symptom is a tacky, uncured skin on the face that matters most. It cannot be rescued; the block is scrap. This is why we ask what your master is made of and what has been on it, and why we test-patch anything we are unsure about before committing four kilos of silicone.
All three resins below are two-part polyurethanes cast under pressure. The differences that matter day to day are pot life and how much detail the resin will pick up before it starts to gel.
| Resin | Mix | Pot life | Demold | Character |
|---|---|---|---|---|
| Standard fast | 1:1 by volume | 2.5 min | 25 min | Cream, hard, crisp. The default for kit parts |
| Slow-set | 1:1 by volume | 7 min | 90 min | For large or thin-walled parts where the fast resin gels mid-pour |
| Tough grade | 100:90 by weight | 4 min | 60 min | Slightly flexible; for pegs, thin blades and parts that get handled |
We cast in cream, grey and black. Pigment is added by weight at under two percent, because past that the resin loses edge definition and the cure slows unpredictably. If you need a specific colour for a display piece rather than a paintable kit, say so at quote stage — it changes the resin, not just the pigment.
Parts are hard enough to fettle within an hour and dimensionally settled within about a week. That week matters if the part has to fit another part. For multi-part kits where the joints are tight, we hold the first pulls seven days and re-check the fit before the rest of the run goes ahead.
Polyester and epoxy casting resins, food-safe compounds, and anything requiring certification for skin contact. Not because they are difficult, but because running them occasionally is exactly how a shop produces one bad batch a year. Those jobs go elsewhere, and we are happy to say where.