Exploding silicone? Orange peel looking resin?

[Jynxia]

Hey docs,
Sorry if this topics been discussed before but I couldn't find anything for it.
I'm trying to cast dolls to sell but for that I'd like flawless casts. I've poured my very first batch of resin recently (Exciting ) but they all tend to have a bites in them or a weird orange skin texture with not one successful clean cast.

I know to guarentee flawless casts I should invest in a vacuum chamber but currently I dont feel like I can make that £200+ commitment. A shop nearby called Tirantis will rent out a vacuum for £85 a week but it's also said on the Smooth-On site that if you haven't degassed your silicone the small bubbles trapped inside will force it to implode when pressurised. I've worked very hard on these moulds and used about 4kg of silicone so I'd like some advice first before I use up more money.

Edit- materials used :

Smooth-Cast 305
Tirantis silicone T28
Smooth On Mould Max 30

Thanks for reading,
Jynxia

[mangozac]

Hi Jynxia welcome to RA!

So what technique have you used for your casting so far? Is there any chance you can take a photo of the "orange peel" results you're describing? It sounds like the reverse of casting under pressure with a room pressure cured mould, which is odd...

[Jynxia]

Thanks for replying Mangozac,

I mix both parts in plastic cups (separate cups, both in one cup, then both in the other) made specifically for this, mixed with a wooden stirring stick which I'm sure was dry, then injected into pour holes. Once theyre in, I sit around poking and wobbling the moulds for a few minutes then wonder off for the 30min curing time. I've casted the head 3 times already and the best one has been when I squeezed and poked it for awhile but even that still had little bites.

Just to make clear, I was only thinking about using a vacuum chamber because of my poor results and I've not even handled one yet. Im currently too worried about my non-degassed moulds exploding or something

Edit: I'll take pictures soon. It's a rough texture because there are bubbles emerging through the surface.

[mangozac]

Oh so hang on the texture is protruding from the part? And you're not using pressure casting? I think I really need to see a picture

[Munkey Joe]

I noticed that you mention you ensured the wood stick was dry, but in my head this is what it sounds like to me.....

I had something similar happen with some OLD resin I had found and had gotten "contaminated" with air moisture. They were 1/2 used and closed up and left for a while (months), and when I found them and started to cast everything I made had and odd texture that I can describe as "orangepeel". Pics would be VERY helpful.

[Magnetic Duckling]

I also demand pictures ^_^
Doll for sale hmmm, are you on The Joint?
If you stay here you will end up getting pressure pot and vacuum, believe me =p

[Anvils Hammer]

£200 is nothing.. try £2000

We really need photos, of everything.

You dont need to mix the resin in two cups really.. its too much faffing around. also If you buy a roll of metal garden wire its cheap and can be curled and snipped to make really awesome mixing sticks which will not interfere with the resin.

AH

[shiphorns]

[mangozac]

That's a good explanation Shiphorns, but I will point out that degassing the silicone using vacuum isn't the only way. I used to do that in the past but these days I simply cure the silicone/master under the same pressure that I will be casting at (just under 60 PSI). That way one can get away with pressure casting without needing a vacuum pump just to make the mould.

Of course it depends largely on the actual silicone product being used. The curing at pressure is most effective because Pinkysil has a very short cure time (around 30 minutes). Silicones with a much longer curing time may present issues keeping them at pressure for long enough.

[shiphorns]

[Anvils Hammer]

[mangozac]

[Jynxia]

Sorry about the long wait. Just finished off all my essays for the year ^^






Here it is. Was orange peel the right way to describe it? This ones my cleanest cast and it's still not smooth and no where near professional. Theres little bubbles under the surface too. Would more sprues do it? I'll try again today as I've got the weekend free.

Complete newbie here so forgive me of anything sounds silly!

[Jynxia]

Magnetic Duckling; I'm on the Joint. I don't plan on showing my face there again until I get this right though. XD Either I'm going to have a nice welcome back or everyone would have forgotten about me and won't care anymore.

Shiphorn: Thank you for explaining it to me. In fact, I did use the bombs-away method, or pouring a VERY thin stream from a height into the corner of my moldbox so I'm sure no bubbles exist near my master's negative.

Thanks everyone for replying so far. Ill post more results soon.

[mangozac]

Orange peel probably isn't the best description

The holes on the bottom of that top piece are just from bubbles pouring the resin. You may want to dust the mould with talc to prevent that from happening.

The "pock mark" problems with the spherical part are quite odd. They are caused by large bubbles just under the surface right? Perhaps you need to tap and agitate the mould a bit after pouring the resin to help release the bubbles?