SPR 201 CC Clear Casting Resin data sheet (PDF)Ask for a quote
Casting with polyester, in one paragraph
A casting resin is poured into a mould and cures into a solid article, with no glass reinforcement doing the structural work. Polyester casting resins do this through a free-radical reaction: a peroxide initiator, activated by a cobalt accelerator, links the polyester chains through the styrene they are dissolved in. The reaction gives off heat, and in a casting all of that heat is generated inside one solid mass.
SPR 201 CC is the clear casting grade of Samrat Poly Resins’ orthophthalic SPR 201 series. It is supplied without accelerator, so the caster adds both the initiator and the cobalt — separately — when the pour is prepared.
Why a separate casting grade exists
The 2026 catalogue gives SPR 201 CC the same typical liquid values as SPR 201 GPC, the general laminating grade: 350–450 cPs viscosity, gel time under 8 minutes and 33–40% styrene. What separates them is the job each is listed for. CC is catalogued for statues and idols, decorative articles and artefacts, and furniture top coats; GPC is catalogued for glass-fibre lay-up and moulding.
For a buyer, that listing matters. It tells the technical team which questions to ask — about section thickness and finish rather than glass content and laminate schedule — and it keeps casting enquiries separate from laminating ones.
Polyester and epoxy casting are different materials
Clear casting is sold in two chemistries, and they are not interchangeable. Epoxy casting systems are two-part: a resin and a hardener mixed at a fixed ratio, curing by a different reaction and usually more slowly. Polyester casting resins are one resin with a small dose of initiator and accelerator, and they typically gel far sooner.
Instructions do not transfer between them. A pour depth, mix ratio or cure schedule written for an epoxy says nothing about SPR 201 CC, and the reverse is equally true. Samrat Poly Resins supplies both routes as separate products — see the polyester and epoxy casting comparison for how to choose between them.
What decides whether a casting works
Section thickness comes first. The gel time published for a resin is measured on a small laboratory sample; a large casting holds its reaction heat and behaves as a different system. Thick pours, sudden changes in section and embedded objects are where casters meet cracking, distortion and heat discolouration.
Colour and filler come second. Pigment pastes, metallic powders and mineral fillers each change how clear the article is, how fast it cures and how much heat it builds. A trial with a clear sample says little about a coloured idol.
The mould comes third. Rubber, FRP and metal moulds release differently and draw heat away at different rates, so the trial should be poured into the production mould or one made the same way.
What the catalogue does and does not tell you
The catalogue publishes four liquid-resin values for SPR 201 CC — appearance, viscosity, gel time and styrene content — together with a reference cure of MEKP 1.5% and cobalt octoate 0.4%. It does not publish hardness, heat resistance, shrinkage or outdoor weathering data for the grade.
That shapes the right questions. An indoor decorative article and an outdoor statue are different requirements, and the second deserves a direct conversation with the technical team before the grade is chosen.