Thanks. This is helpful. I want to keep the electronics alive within the 
resin. I know if can be done because this is standard practice for LED 
manufacture after all, what is a 5mm LED but a die, some aluminum and an 
acrylic encapsulation?. I did a bunch of live embedments a few years ago 
- the encapsulated electronics are still working fine the but the units 
never cured and some are still tacky (water-clear urethane in a silicon 
mold - perhaps not the best combination).

It's the deal toy guys that gave me the 375 degree number - I agree - 
seems excessive.

Alden


Jinx wrote:
>>> I'm looking for a way to cure water-clear casting resins at low 
>>> temperatures. The typical process (if you talk to the "deal toy" guys) 
>>> is 6 atmospheres of pressure in an oven, with about 2 hours of 375 
>>> degrees (F) along with some gentle ramp up / down time. They seem
>>> to de-gas using pressure, not vacuum. Supposedly some dental molding 
>>> processes use a UV process instead of heat. I'm trying to come up with
>>> a process that I can do myself that will not require excessive equipment 
>>> or hazard
>>>       
>
> 375 seems way excessive to me. I've done a lot of clear casting with polyester
> and often heat is the one thing you need to avoid, but that depends greatly on
> the volume and contents. Room temperature, 20C, is mostly adequate
>
> A couple of examples
>
> http://home.clear.net.nz/pages/joecolquitt/coaster.jpg
>
> http://home.clear.net.nz/pages/joecolquitt/pyrites.jpg
>
> The coaster is 97 x 8mm, which is a lot of surface area to lose heat from.
> If this was a plain chunk of resin I'd just put it in the warm box - about
> 40C - and let it do its thing. But the IC insert has a higher coefficient of
> expansion than the resin and there's a danger of silvering. This is when the
> object heats and expands during the curing phase and then contracts away
> from the resin when it cools, leaving a void. To avoid a void and unwanted
> bubbles, pre-coat the object and insert it after that coat gels. This is the
> best method with something like a bug or IC a thermionic valve which has
> a lot of fiddly bits that can trap bubbles. The other problem with once-live
> material is that any moisture left inside can evaporate and cloud the resin
>
> The pyrites example is 50mm high and is a reasonably bulky casting. Once
> again, excess heating should be avoided. For the insert reason above and
> also because if the block of resin overheats it can pull itself apart. The centre
> can get very hot, depending on catalyst level, whilst the outside is cooling
>
> A large pour with too much catalyst can catch fire, I've seen it happen. It's
> possible, but tricky, to do a large encapsulation in stages. They tend to be
> cooled rather than heated
>
>   

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