FREQUENTLY ASKED QUESTIONS

The short answer: because they last significantly longer and produce significantly better results. Castaway moulds use platinum-cure silicone sourced from EU and UK manufacturers — not the cheapest available, but the most consistent and traceable. The rigid 3D-printed support frame is included as standard, which cheaper alternatives don't offer at all.

On a cost-per-cast basis, Castaway moulds typically work out cheaper than budget alternatives. A £20 tin-cure mould lasts around 25 casts — that's £0.80 per cast. A Castaway platinum mould used for 100 casts works out at significantly less per piece. The upfront cost is higher. The lifetime cost is lower.

Even high-quality platinum silicone will deform under the weight of a wet Jesmonite or concrete pour without external support. The frame wraps the silicone precisely, holds its geometry during filling and cure, and keeps it stable on a vibration plate. Without the frame, the mould would sag, producing asymmetric pieces with inconsistent wall thickness.

The frame also dramatically extends mould life — a supported mould under no stress lasts far longer than one that deforms and recovers with every use. Every Castaway mould ships with the frame fitted. It's not an add-on. It's part of the product.

The speed clips are colour-coded by mould size — red for small, blue for medium, green for large. It's a system designed so you can identify your mould category at a glance, without checking a label or product description. The clip colour also appears on all Castaway product photography and packaging.

The clips themselves are 3D-printed in the UK, bespoke to each frame size. They lock the frame halves together with a single firm press and release just as quickly — no tools needed.

You don't need one, but we strongly recommend one. Without vibration, trapped air bubbles create surface pitting and voids in your finished piece. The Castaway rigid frame is specifically designed to sit stably on a vibration plate — this is an intentional design decision, not an afterthought.

If you don't have a plate, tap the assembled mould firmly on your work surface 20–30 times immediately after pouring. Entry-level vibration plates start from around £30–40 online and make a significant, immediately visible difference to surface quality.

Use the Castaway Jesmonite Calculator — it gives exact powder and liquid quantities by weight for every mould in the range. You'll find it in the Technique Guides section. It also has a terrazzo mode that accounts for aggregate by weight.

As a general rule, always mix slightly more than you think you need. Running out mid-pour and having to mix a second batch introduces a visible join line and inconsistent colour. A small amount of wasted material is a much better outcome than a spoiled piece.

Surface pitting is almost always caused by one or more of the following: air bubbles not removed by vibration, mix poured too quickly introducing more air, or mix too thick to allow bubbles to rise. In most cases, increasing vibration time to 90 seconds and slowing the pour speed resolves the issue entirely.

If you're getting pitting in the same area on every cast, it's likely a low point in the mould where air collects. Try tilting the mould during filling so that area fills last, then vibrate immediately.

All Castaway moulds use platinum-cure RTV silicone sourced exclusively from EU and UK manufacturers. We choose our suppliers based on quality, consistency, and traceability — not price. Every batch is traceable from raw material to finished mould.

This matters for quality reasons — premium EU and UK-sourced platinum silicone maintains consistent Shore hardness between batches, so every mould performs identically. It also matters for sustainability and ethical sourcing reasons. We know who makes our materials and how.

After each cast, wipe the silicone surface with a damp cloth to remove any residue. Mild soap and warm water is fine if needed — avoid solvent-based cleaners, as they degrade platinum silicone over time. Never use acetone, white spirit, or similar products near the mould.

For storage, always keep the rigid frame fitted around the silicone. This prevents deformation during storage. Store flat, away from direct sunlight and heat. Properly maintained, a Castaway mould should last well beyond its rated 100-cast lifespan.

Yes — Castaway moulds are fully compatible with epoxy resin, polyurethane resin, concrete, plaster, and Jesmonite. Platinum silicone releases cleanly from most resin formulations without requiring a release agent, though we recommend doing a test cast with any new resin product before committing to a full pour.

One important note: never expose platinum silicone to tin-cure silicone, latex, or materials containing sulphur compounds — these cause cure inhibition and will permanently damage the mould surface.

UK orders are dispatched within 1–2 working days and typically arrive within 3–5 working days of ordering. Free delivery is available on all orders over £50. We use tracked shipping as standard — you'll receive tracking information as soon as your order is dispatched.

Each mould is packed with the frame assembled around the silicone for protection in transit. The packaging is sized to the product — we don't use excessive packing materials. The usage guide is included inside the box.