Materials and compliance
Material choice is where most concrete mould failures are decided, usually before anything is cast. These are the families we work in, what each is genuinely good at, what will poison it, and what comes with an order.
Start here
A softer mould flexes out of deep relief and undercut. A harder mould holds dimension across a long run and survives a working yard. Nothing does both well, which is why we ask what you are casting and how you strike it before quoting.
The ranges on this page are indicative starting points for a conversation rather than a specification. The material recommended for your job is recorded against your order with its hardness, batch, backing detail, so a replacement liner in two years is made from the same thing rather than from whatever is closest at the time.
Where a figure genuinely depends on the job, such as expected casts, strike time or tolerance across a panel, we say it depends and then say what it depends on. That is a less impressive way to write a materials page and a more useful one to buy from. The route the material goes through is on how each moulding route works on concrete.
Mould material families
Indicative material guide
| Material | Typical Shore hardness | Best suited to | Watch out for |
|---|---|---|---|
| Platinum-cure silicone | Shore A 20 to 60 | Formliners, fine texture, deep relief, heritage detail, long library life, dimensionally stable repeat panels | Cure inhibition from sulphur clays, tin, amines, latex, uncured resin. Patch-test every pattern |
| Tin-cure silicone | Shore A 20 to 40 | Plaster, cast stone and general concrete work, and moulding contaminated or unknown originals where platinum would be poisoned | Alcohol by-product, around 0.3% shrinkage plus long-term creep, so a shorter useful life than platinum |
| Polyurethane rubber | Shore A 30 to 80 | Abrasive wet-cast concrete, kerb moulds, paving moulds, high-wear repeat production where the face is not delicate | Moisture-sensitive during cure, less forgiving on very fine detail, needs a compatible release |
| Rigid polyurethane and epoxy | Shore D 70 to 85 | Patterns, pattern plates, mother moulds and jackets behind a flexible face | Rigid by design, so no undercut release at all and proper draft is essential |
| Resin and glassfibre backing | Structural, no Shore figure | Backing shells and ribbing behind formliners and GRC mould faces | Must be fully cured before a platinum silicone face is cast against it |
Hardness ranges above are indicative and pending technical review. Treat them as the start of a conversation. The final specification is confirmed in writing with your quotation, against your mix and your release regime.
Hardness, measured
Shore A is read with a durometer on a stand, pressed into a flat slab of the cured material. It matters twice over on concrete work. A softer face picks up finer texture and comes off relief that would tear a harder liner. A harder face holds its geometry across a long run and survives being handled in a working yard. You cannot have both at once, so the figure is chosen against your relief depth and your strike sequence rather than against a catalogue.
Whatever we agree gets recorded against the order along with the material and the backing detail, so a replacement liner in two years is made to the same specification rather than to somebody's memory of it. The ranges on this page are indicative and pending technical review, and the figure on your order is the one that counts.
Silicone or polyurethane
Both cast concrete. They fail in different ways and they are quoted on different pour counts, which is what makes the choice a commercial decision rather than a taste one.
Scroll sideways to see the whole diagram.
Scroll sideways to see the whole diagram.
Cure systems
This one table explains most of the price difference between two liners that look identical on the bench.
Platinum (addition) against tin (condensation) cure
| Property | Platinum cure | Tin cure |
|---|---|---|
| Cure by-product | None | Alcohol given off as it cures |
| Shrinkage | Under 0.1% | Around 0.3%, plus slow long-term creep |
| Dimensional stability over many casts | High, the reason it suits repeat panels | Drifts with age, so a library mould loses accuracy |
| Library life | Long | Shorter |
| Tolerance of contamination | Poor. Inhibited by sulphur, tin, amines, latex, uncured resin | Good. Will cure against surfaces that poison platinum |
| Cost per litre | Higher | Lower |
| Curing against the other system | Will not reliably cure against a tin-cure surface | Will cure against a platinum-cure surface |
The last row catches people out when re-moulding from an old tool. It is a one-way door, so plan the sequence before you commit material.
Choosing a material
Wet-cast concrete, semi-dry cast stone, GRC, fibrous plaster, resin. Each one attacks a mould face, shrinks and releases quite differently. Aggregate size and cement content change the abrasion picture. This is the single biggest driver of material choice.
Table vibration works the face against the mix, and accelerated or steam curing adds heat on top. Together they age a liner far faster than the same number of quiet ambient-cured pours, so the curing regime belongs in the enquiry.
By flexing the liner, by lifting the unit, on a tilting bed, by crane. The release method sets the hardness and tear-strength requirement more than the geometry does, and it settles the question of a softer face locally around an undercut.
Silicone often needs no chemical release from concrete at all. Where an agent is used it has to be compatible, because petroleum-based and reactive agents swell or degrade a silicone face. Tell us what you spray and what you wash with and we will check it.
Rigidity
This is the single most common specification error we see. A deep formliner or a GRC mould with nothing rigid behind it bows under the pour or moves under a roller, and the geometry drifts across the run. The failure is gradual, which is worse. Nobody notices until the panels stop matching.
So the backing is engineered with the face. Plywood for flat repeat liners, welded steel where the loading or the span demands it, a resin and glassfibre backer with ribs for curved and developable surfaces. One detail worth flagging. A glassfibre or resin backer must be fully cured before a platinum-cure face is cast against it, or the face will not cure where it touches.
Commercial terms
Included as standard
| Item | What it means |
|---|---|
| Written warranty | Every mould is covered against manufacturing defect, with the material, hardness plus backing specification recorded against your order. |
| NDA by default | We work under non-disclosure as standard. Your drawings, artwork, survey data and patterns are not used for anyone else. |
| Retained patterns | Patterns are stored so a replacement liner or an additional mould matches the original rather than being re-engineered. |
| Recorded specification | Material, hardness, batch, plus backing and joint detail are held against the order, so a repeat in two years is genuinely a repeat. |
| Patch test and trial | We test for cure inhibition against your pattern and check release-agent compatibility before production tooling is committed. |
| Handling guidance | Cleaning, storage plus stacking guidance goes out with the tool, because it affects tool life more than most people expect. |
| Named engineer | One technical contact from enquiry through to repeat supply. |
Approvals and accreditations
We hold no third-party approvals or accreditations that are relevant to advertise here, and we are not going to imply otherwise. We will tell you what a material can be specified to and supply the manufacturer's documentation for it. Where your specification requires a particular approval, tell us at enquiry stage and we will say plainly whether we can meet it. No ISO number, no scheme membership, no test certificate is claimed anywhere on this website.
Frequently asked
Platinum-cure addition silicone has no cure by-product, shrinkage under 0.1% and stays dimensionally stable over many casts, so it is the choice where a long library life and repeatable geometry matter. Tin-cure condensation silicone gives off an alcohol by-product, shrinks around 0.3% and keeps creeping slowly afterwards, which shortens its useful life. It is cheaper, and it tolerates contaminants that would poison a platinum system. For a weathered original with unknown residues on it, tin cure is often the pragmatic answer.
Sulphur, tin, amines, latex, uncured polyester and uncured epoxy resin all inhibit addition cure. On a construction job the realistic culprits are sulphur-bearing modelling clay used to build a dam, old release agent on a pattern, latex gloves, and resin in a backing shell that has not fully cured. The symptom is a tacky uncured skin against the contaminated surface while the rest of the mould cures normally. We patch-test every time, because the cost of testing is trivial next to a failed pour on a scaffold.
There is a one-way door here worth knowing about. Tin-cure silicone will cure against a platinum-cure surface. Platinum-cure will not reliably cure against tin-cure. So if you have a tin-cure master or an old tin-cure liner and you want a platinum-cure production tool from it, tell us. The sequence has to be planned, and in some cases an intermediate pattern is the only clean route.
Indicatively, softer material around 20 to 30 Shore A for deep undercut and heritage detail, where you have to flex the mould off the unit. Harder material around 40 to 60 Shore A for flat repeat panels, where dimensional stability across many casts matters more than flexibility. Those are starting points for a conversation. The final figure is confirmed in writing with your quotation, against your mix and your release regime.
You get a written warranty against manufacturing defect, the recorded material and hardness specification, the batch and the backing specification. We can also tell you what a material can be specified to and supply the manufacturer's own documentation for it. What we will not do is issue approvals or accreditation certificates we do not hold. If your specification demands a particular third-party approval, say so at enquiry stage and we will tell you plainly whether we can meet it.
Clean, dry, flat, out of sunlight, supported so the face carries no load, and never folded against itself. Storing a liner damp keeps alkaline residue in contact with the face. Storing it under weight puts a memory into the rubber that shows up in a panel later. Handling and storage guidance goes out with every tool, because it changes tool life more than most people expect.
One group, four specialisms
Material knowledge is shared across the group. The same technical team advises all four divisions, so a release problem solved for TCI Culinary can end up fixing a precast bed.
Technical question?
Tell us what you are casting, how you compact and cure it, how you release it and what you wash it with. We will recommend a material and explain the trade-off you are accepting.
