Route two of five · the workhorse
A boxed silicone mould is cast around a finished master, with the split line deliberately chosen rather than simply accepted. This is the route used for most candle, homeware, plaster and resin work, and it copes best with an undercut worth keeping.
Three arrangements
It is the same material, wrapped around the part in three different ways. Your part's shape decides which option suits it, not the price list.
The master sits in a box, and silicone is poured over it in one go. This creates one piece with a single opening and no visible parting line. It works only when the part can be pulled from a single cavity, so it is best suited to shapes that taper towards the open face. Deep vertical walls can grip the mould, making removal a struggle every time.
Hand-made moulds
Cast in two halves with keys, so they register the same way every time. This is ideal for anything with detail on both faces, or for a form that will not release from a single cavity. You accept a witness line where the halves meet, and we position it where the part will not be judged.
Compare the routes
This approach uses a thinner silicone skin taken tight to the part and supported by a rigid jacket. The skin flexes away from features that would lock a solid block, helping ornate and undercut work come out intact. It is more fragile, takes longer per part to use and will not withstand careless handling.
Hardness and releaseBoxing and split line
Much of the skill behind a cast mould comes before any silicone is mixed. The master is sealed, keyed and boxed, the split line is set, and the orientation is chosen so air has somewhere to go when the pour begins.
If the split line is wrong, every part can show a visible line across the face your customer sees. Worse, the two halves may shift and leave a step. If the orientation is wrong, air can remain trapped in fine detail as a permanent void that no amount of trimming can hide.
This is also where we decide the wall thickness. If it's too thin, the mould distorts under the weight of what you cast into it, leaving parts thicker on one side. If it's too thick, the mould is heavy, slower to work with and unnecessarily expensive.
If your part has fine relief or lettering that needs to come out cleanly without touching up, we pour it under vacuum instead. This is vacuum casting: the same discipline, with the air removed rather than avoided.
Repeatability
A cast mould is a consumable, so it will wear over time. Whatever you pour into it can subject it to chemical attack. Eventually, it may go soft, tear at a thin corner or stop releasing. That is normal and does not mean there is a fault.
What makes a replacement match the original is not the mould, but the master. We keep the master pattern and its recorded grade, so mould four is made from the same geometry as mould one, rather than from a part produced by mould three. Copying a copy is how a range can slowly drift out of shape.
Here are the honest limits of this route. It is not the cheapest option per part once you are producing at higher volumes. The surface finish depends on the finish of the master, rather than the silicone, and a crisp arris will not last as long as it would with a hard tool. Cast moulds are for casting materials into, not for making silicone parts.
If you buy the same item in quantity year after year, the numbers can start to favour compression or injection. We prefer to tell you that rather than sell you a queue of soft moulds.
To quote it
A physical sample is ideal because it answers questions a drawing cannot. A photograph with a rule in shot is enough to get started. If you have neither, we can make the master.
Whether you choose wax, plaster, resin, concrete, soap or chocolate, the material sets the grade, release behaviour and whether food-contact paperwork applies.
It is not the total for the year that matters, but how many pulls happen before the mould gets a rest. That has a greater effect on wall thickness and hardness than anything else.
A maker who owns the piece will flex a thin mould carefully. A production operator at the end of a shift will not. Tell us who will use it, and we will build your mould for that.
Send us a part and we'll quote for it
At a glance
How a two-part mould fits together
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From idea to finished mould
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Ready to start?
Send us a drawing, photograph or sample. We'll come back to you with a mould strategy, a material recommendation and a price.
Real people, a real workshop
No call centre and no middlemen. When you contact TCI Mouldings, you speak to the team who design, build and check your mould.
Thomas LaneManaging Director
George PrestonDesign & Project Manager
Kelly BallingerHead of Partnerships
Jim AndertonProduction Manager
TheodoreEmployee Welfare