Vacuum vs Pressure pot

[piecemaker]

Good silicone is also key, don't buy cheap crap...I have molds that are 8-10 years old, but they are made from good silicone. The two best in my opnion are Dow Corning V and Dragon Skin 10 from Smooth-on... I use the Dragon Skin 10 quick set (75 minute set time)... The Dow Corning is a better product for longevity but it's more expensive and takes longer to set up. Dragon Skin is cheaper, easier to get, and works great for one and two part molds.

-Dave

When i first started i was using the OOMOO stuff from Smooth-On.Then i switched to MicroMark One to One/Rapid.Dragon skin seems to be about 10.00 bucks cheaper than that.I know more expensive doesn't always translate to better.I'am going to try the Dragonskin,cheaper+better= win/win.Thanks.

[David Lee]

Awesome,i will definately be trying this first before buying another vacuum pump.If i can accomplish the same thing with just a pressure pot,thats the way to go.Thanks.

Good silicone is also key, don't buy cheap crap...I have molds that are 8-10 years old, but they are made from good silicone. The two best in my opnion are Dow Corning V and Dragon Skin 10 from Smooth-on... I use the Dragon Skin 10 quick set (75 minute set time)... The Dow Corning is a better product for longevity but it's more expensive and takes longer to set up. Dragon Skin is cheaper, easier to get, and works great for one and two part molds.

-Dave

[piecemaker]

Not trying to bust any bubbles (sorry I couldn't resist it...).

You can in fact pressurize your molds as you make them, no de-gassing needed... then using the same tank pressurize your cast... I am sure de-gasing your silicone is a great thing to do, never tried it, but it is not necessary to get perfect bubble free molds or casts...

Been doing it 13 years and I get flawless molds and casts... Now having said that, if you don't pressureize your molds when making them, you CANNOT, cast resin in them under pressure this will cause the resin to seek out surface weak spots (caused by air bubbles) and give your piece little round zits all over it...

Pressure tank is really all you need IMHO.

Dave

Awesome,i will definately be trying this first before buying another vacuum pump.If i can accomplish the same thing with just a pressure pot,thats the way to go.Thanks.

[David Lee]

Not trying to bust any bubbles (sorry I couldn't resist it...).

You can in fact pressurize your molds as you make them, no de-gassing needed... then using the same tank pressurize your cast... I am sure de-gasing your silicone is a great thing to do, never tried it, but it is not necessary to get perfect bubble free molds or casts...

Been doing it 13 years and I get flawless molds and casts... Now having said that, if you don't pressureize your molds when making them, you CANNOT, cast resin in them under pressure this will cause the resin to seek out surface weak spots (caused by air bubbles) and give your piece little round zits all over it...

Pressure tank is really all you need IMHO.

Dave

[piecemaker]

Ah! yeah, that makes sense... where even small internal bubbles can become a big issue, akin to casting in fine metals.

Yeah,internal bubbles are a bad thing.Another issue i've had is when sanding on some resin parts you expose internal bubbles making them external bubbles that you then have to deal with.I gotta go bubble-free! Thanks for your help.

[Confessional]

Ah! yeah, that makes sense... where even small internal bubbles can become a big issue, akin to casting in fine metals.

[piecemaker]

I would:
1.measure and degas both parts A and B
2.mix and degas
3.pour and degas
That works best with the longer setting silicone. If it cures fast you don't have time for all the degassing. Silicone with a shore of 10 works best! The softer the better. I recommend dragon skin 10 from smooth-on.

Thanks,i may have to try Dragon skin.I'm not sure the shore of the stuff i'm using right now,it will actually setup in about 3 hours.Thats the reason i liked it.

[piecemaker]

I'm still learning too, but in most cases if you mix silicone properly and poured it carefully there shouldn't be any need for degassing... meaning what bubbles exist will naturally release. Lots of variables I know, but I was taught by someone who makes molds for things big and small, casts in a variety of materials and really has instilled quality control in my process.

That said, there's some good tips in this set-up that might be helpful: http://www.squidoo.com/how-to-build-...-for-degassing

I dont really have a problem with how i'm doing it now.Most things turn out fine.I hoping this will help with some more intricate castings and i also want to cast some stuff in clear and translucent resins and want them to be as bubble-free as possible.

[LonnieFisher]

I would:
1.measure and degas both parts A and B
2.mix and degas
3.pour and degas
That works best with the longer setting silicone. If it cures fast you don't have time for all the degassing. Silicone with a shore of 10 works best! The softer the better. I recommend dragon skin 10 from smooth-on.

[piecemaker]

I'm still learning too, but in most cases if you mix silicone properly and poured it carefully there shouldn't be any need for degassing... meaning what bubbles exist will naturally release. Lots of variables I know, but I was taught by someone who makes molds for things big and small, casts in a variety of materials and really has instilled quality control in my process.

That said, there's some good tips in this set-up that might be helpful: http://www.squidoo.com/how-to-build-...-for-degassing

Thanks for the link.It looks like i'm going to need a bigger vacuum pump.

[piecemaker]

If you don't vacuum degas your silicone, you can't pressure cast your resin.

Thanks Lonnie,thats what i wanted to know.I'll give my vacuum chamber setup another try but will degas/vacuum the silicone before mixing,after mixing and then as it cures.Then pressure pot the resin in that mold.

[boss]

Lonnie's right. Degas before pouring your rubber on the part.

[Confessional]

I'm still learning too, but in most cases if you mix silicone properly and poured it carefully there shouldn't be any need for degassing... meaning what bubbles exist will naturally release. Lots of variables I know, but I was taught by someone who makes molds for things big and small, casts in a variety of materials and really has instilled quality control in my process.

That said, there's some good tips in this set-up that might be helpful: http://www.squidoo.com/how-to-build-...-for-degassing

[LonnieFisher]

If you don't vacuum degas your silicone, you can't pressure cast your resin.

[Confessional]

^^ Anti-Bubble 101: Super smooth & level mold form (clay) box, ample spray of release, pour your mold from the lowest/deepest point with a steady steady flow/stream, turning on the fill, and if you have vibration plate (or can rig up a similar action) they work great. Some materials can be temperature sensitive as well leading to slower releasing bubbles.