Obviously I am new here, but I have thoroughly enjoyed reading through many of the threads. I am in the early stages of designing and building a fairly large product (roughly a 12in cylinder ~ 30in tall) made from clear resin. I had planned on building the molds from a combination of metal/wood/fiberglass and RTV silicone for hand pouring a clear finished product. The product will be low volume (<1k units/year) and is aimed at aquarium hobbyist. I have built smaller molds from all of the above materials for various resin castings in the past, but never anything this large; and I have never cast clear resins. Because optical clarity is fairly important, I am certain that I am going to waste a lot of resin in the ‘learning process’

I am familiar with vacuum de-gassing, slow cycle times and post cures. Selecting a resin is an area where I could really use some input. There are polyester resins, epoxy-resins and urethane resins that all purport to be ‘crystal clear’. I have cast non-clear versions of all of the above, and my best results were with epoxies and urethanes. Constant contact with water and potentially ozone will probably preclude polyester based resins, though if this is a bad assumption, please point this out. The wall thickness of the parts will be ~1/4in to 1/2in. Structurally there will be little stress or pressure on the finished product.

Additionally if any here think that building molds suitable for acrylic (eg. Perspex) might be a viable option even in the early stages, then I would be interested in hearing the ‘pros’ and ‘cons’ of that route. My assumption is that the cost of the molds would initially preclude this option for such a low production volume. I can fabricate molds suitable for casting resins, thus keeping the costs reasonable, but the industrial quality molds that Perspex would require are likely beyond my capabilities.

This project will be more on the DIY level than an industrial approach to begin with. I have a mill-drill, a couple small lathes and other basic shop tools, but nothing that would impress any machinist. My goal is to use low-tech, low-cost molds for the first year or two of the product, and then if volume justifies it, moving to a higher production mold/process.

Thanks In Advance for any input,

Fish