udog
Well-Known Member
I finished the mold with the T4 40d shore Xiameter silicone I have. As temps are rising here to hot summer I put in the mold to cure in the fridge to slow down the curing time which seemed to work ok, as I got a bubble free mold. I can see some bubbles around, but none touching the model. Good.
Also, the thin parts seem to stand better till the moment, better castings in general. And the back seam line is tighter with the higher shore too. The downside is that demolding is tough as it´s a block mold with a slit cit in the back and the silicone is much harder. All in all good, and I save some money having some kgs of this silicone here. And no pimples!
I´m tinting "drop by drop", which I know might be risky some times, but it´s working till now.
I could make a bigger box but not sure my degassing chamber will be big enough, specially for the 2kg molds (big model). I have to degas the silicone (prior to pouring) kg by kg or it will flow out of the container. I do have a bigger chamber, but yet to be prepared to work a as a degassing chamber,
I have one question about pressurizing. How long do you have your resin under pressure.?. I try to turn it off when I see it starts gelling. ¿At what pressure?. I´m in five now, lowered it down from six to five due to the softer silicone. Seems to work fine, although sometimes when sanding down the "pimpled castings" an anoying small bubble appears here or there,
Have to try degassing the resin too, haven't done so yet. What worries me about this is high temperatures plus degassing boiling might shorten the working time, which is already happening due to summer itself, makes me have to move fast. Might have to cool the resin down in the fridge to do so. Must test.
Thanks for all the feedback and interesting comments.
Also, the thin parts seem to stand better till the moment, better castings in general. And the back seam line is tighter with the higher shore too. The downside is that demolding is tough as it´s a block mold with a slit cit in the back and the silicone is much harder. All in all good, and I save some money having some kgs of this silicone here. And no pimples!
Good advice, thanks. I´ll try that. But I´m still not confident because of the colour, Not sure that mixing one or two hours before will avoid the tint going down again (it does so fast).The other thing, and this is what I have settled on is to shake the resin really good an hour or two before I will be pouring.
I´m tinting "drop by drop", which I know might be risky some times, but it´s working till now.
You can also pour the silicone in the mold box and vacuum degas again if your mold box is big enough.
I could make a bigger box but not sure my degassing chamber will be big enough, specially for the 2kg molds (big model). I have to degas the silicone (prior to pouring) kg by kg or it will flow out of the container. I do have a bigger chamber, but yet to be prepared to work a as a degassing chamber,
I have one question about pressurizing. How long do you have your resin under pressure.?. I try to turn it off when I see it starts gelling. ¿At what pressure?. I´m in five now, lowered it down from six to five due to the softer silicone. Seems to work fine, although sometimes when sanding down the "pimpled castings" an anoying small bubble appears here or there,
Have to try degassing the resin too, haven't done so yet. What worries me about this is high temperatures plus degassing boiling might shorten the working time, which is already happening due to summer itself, makes me have to move fast. Might have to cool the resin down in the fridge to do so. Must test.
Thanks for all the feedback and interesting comments.