Tin Cure vs Platinum Cure

[csimian]

After searching some threads here it seems that Tin Cure Silicone RTV is used or mentioned more than Platinum Cure. I also read that Platinum Cure for molds can result in longer lasting molds for a higher material cost. If this is true why do people use Tin Cure Silicone? Are they more difficult to work with.

Some background; my main uses for molds will be for miniatures.

Thanks!

[Lane]

Tin cure silicone could be considered the standard grade. It's easy to use and will cure properly in contact with almost anything. The disadvantages are usable life, shrinkage and long term stability.

Platinum cure Silicone has very low shrinkage, can get more castings out of and cured molds have a long shelf life. Unfortunately they suffer from cure inhibition when in contact with some materials. This means you have to be careful what your masters are made of or you end up with a gooey mess of partially cured silicone.

For short runs of parts that can have a small amount of shrinkage (1-2%) tin cure silicone is great.

If you need exact fit ( < .5%), are casting more than 20 copies or cast a few at a time but a couple years apart use a Platinum cure.

[mangozac]

Tin cure is (at least around here) much more easily available, and from what I've heard a fair amount cheaper than platinum cure. That said however, for mass production the platinum cure works out cheaper since the mould should last so much longer.

Hahaha here's something funny: although I started out using tin cure silicone (Barnes Ultrasil), I have been using Bares Pinkysil for a while now. I knew is was quite different to the Ultrasil as it's a 1:1 mix ratio rather than 10:1, but I had never actually thought about what it actually is. The Pinkysil is advertised as an Addition Curing silicone, whereas the Ultrasil is a Condensation Curing product.

I just did some research and it seems that addition curing and condensation curing are equivalent to Platinum and Tin curing respectively! So for quite a while now I've been using platinum cure!

The Pinkysil is about 20% more expensive than the Ultrasil, however like I said it's a far superior product and much longer mould lifespan is achieved with it. I wouldn't go back to the Ultrasil unless I had a requirement for a longer pot life.

Note also that I've never had any curing issues with the Pinkysil, although I've always used a sulfur free modelling clay when making moulds, and the parts I cast are always either metal, resin or styrene, leaving minimal opportunities for the silicone to react with the master part...

[paulson games]

I used the platnium cure from tap plastics and I can't say I was very happy with it.

Their stuff reacts with wood and it inhibits curing, I didn't happen to read that on the label at the time and after 8 hours it was stilla gooey mess. (despite a cure time of 70 minutes) Given how expensive it was I was seriously unhappy. It was also a totall bitch to clean off the masters.

It's super flexible compaired to the run of the mill silicon I use from smooth-on but that also makes it very hard to modify to cut so widdening vents is really tough.

Given that it was almost twice the cost of smooth-on silicon I binned that idea, fortunately I was only into the project for about $50. Totally bad experience, although others may get better results.

[blind pig]

[Lane]

[csimian]

Thanks for the advice! Does anyone have experience with the Smooth-On Platinum Silicone or the Polytek line? Also, what Shore Hardness would you all recommend?

[mangozac]

[Anvils Hammer]

Ive used both types of rubber, and in my experiance the platinum cure I used was DREADFUL.

not only was it harder to get the parts out and left more flash attached to the mold than when using tin cure, but I also found the claimed
"up to 150 casts per mold, much more than tin cure"
to be total rubbish, I got about 30 casts before having to chuck the molds, compared to 40-50 from my tin cure stuff.

This is the resuly of a side by side test using identical molds, made of the two separate materials, I was trialling different rubbers early on when I started Anvil Industry.

Tin cure is cheaper, and better, the only advantage platinum cure has is that is it amazingly easy to mix and pour and the molds had virtually no air bubbles, even without pressure casting the molds which I have to do with my tin cure.

Cheers,

AH

[Lane]

[Anvils Hammer]

[mangozac]

It sounds more like an issue with that brand or something - the rest of us have had far superior results using the platinum cure products...

[Anvils Hammer]

Anyone know any UK suppliers of platinum cure?

Im happy to try another brand before writing it off completely..

AH

[jontidy]

If anybody is casting parts with clear polyester resin then the platinum cure silicone is a better choice as it gives a much clearer surface finish. Although I still have to sand and polish my parts, It now takes half the time as I dont have to start on such a low grit paper. The tin (condensation) cure stuff would give a horrible "aligator skin" surface finish on the clear casting.

[shiphorns]