Casting Anti-bubble advice?

awesome use for an electric toothbrush! cool - i'll have to try that. I have problems with bubbles in small intricate areas (like the tips of ears) - i've been tapping gently after pouring, and definitely it seems better than not pouring....

it was also recomended to pour the mold partly full, then tilt and swirl the resin around to cover all internal surfaces of themold, before finishing pouring.....

 

When I cast resin model kits, I dust the mold with talc, shake out the excess then pour the resin. The talc helps to draw the resin into the tight spots and also acts as a release agent.

 

Ooohhh, an electric toothbrush??!? *takes notes*

Caitlindevi built her own agitator, but I'm not sure what she used . . . I'll have to ask . . . the toothbrush is a *brilliant* idea!!

-- A

 

How about sitting the mold on top of a washing machine while it's on the spin cycle .. that would shake it up LOL. You would have to watch it carefully tho!

 

I'm not sure if doll resin is the same as the resin I use when making jewelry, but after I pour the resin and it sits for a minute or so and the bubbles have risen to the top, I take a drinking straw and gently blow (more like an exhale) on the bubbles and they pop

 

Depending on the size your bubbles, you may also want to consider venting your mold. If you are getting large bubbles where the mold is trapping air in tight areas, it may help to make thin little projections where the air can rise. Also, how you position your mold while you're pouring can help.

When I cast, I usually do the talc method that nepenthes suggested. It does help. Though I don't know if it would be as effective with all types of resin. I also rotate and tap my mold.

The most effective (but most expensive) method of controlling bubbles is to vaccuum your part a and part b before mixing... and if you have a resin that takes more than a few minutes to gel, you can also vaccuum the mixed resin when it's in the mold. This can be really messy though since drawing outt he airbubbles makes the resin froth up like it's boiling! =_=

 

Also, gently mix the resin. You don't want to introduce bubbles while you are stirring.

 

<grin> - I had been reading on another site about vacuming the resin and was terribly confused - envisioning pouring the resin into the mold and having it frothing madly out of the pour holes and couldn't figure out at all how that was going to work...

Thank you so much for explaining vacuming each part before mixing armeleia! (I feel rather challenged now.... <grin>)

Nepenthes, when you say talc, do you think it needs to be specifically talcum powder, or do you think any generic babypowder type thing would work?

doughgirl, you reminded me of a big question - when i've been making a hollow head mold, so I have a silicon plug that sits on top of the totally hollow outside of the head mold - and i've got small holes in it to the topmost part of the desired head --- but pouring the resin is kind of iffy for me. am I being dense? is there a better way to set this up for pouring?

thanks everyone for great info... great idea sand3!!!

 

Baby powder works fine.

 

I have some difficulties getting the silicon plug back in perfectly aligned to make the eyeholes of the outside and the inside mold pieces line up properly. I like the idea of squishing the premeasured resin with the internal mold piece, but am afraid I would still be futzing around trying to line it up perfectly as the resin sets up......

 

patl, did your mold have registration marks/keys? Those will help you line up your mold pieces quickly and correctly every time!

 

urm - hey armeleia,

actually - I did set one key (1 little marble) - but it still allows enough rotation to cause problems. the last pour, the inner eye part hit the outer head part just below the actual eye so i ended up with solid eyes, and almost transparent resin just below the eye - fixable, but frustrating.

do you do 2 keys? and probably something like a square would be better than the sphere, preventing rotation.....

 

I've actually been doing multiple keys... if you have two opposite each other then it can't rotate.

sand - I've cast small heads with a squish mold... it works, but you'll likely end up with bubbles near the headcap... and you'll need to pour carefully (and tap it a lot) to avoid airbubbles getting caught in the high parts of the nose, lips, and top of the ears.

 

I usually cut my keys into the top of the outer mold (using a scalpel) after it is set .. I cut about 4 keys of different shapes around the top of the mold .. then I pour the core mold. This way you can be sure you are aligning the core mold perfectly.

 

As well as talc, They say that heating the mold first so it's warm when you pour enhances its lubrication properties to help the bubbles slip off and stop from sticking.

Other bubbles can arise from moisture, so dehumidifier or crisp Fall day might help.

Lot's of tiny tiny bubbles like fizzing can come from a dye that isn't compatible with your resin.

 

That's what I do too. I found that the "squish" mold works really really well. the thing I'm most wondering about is delicate thin things... like fingers. :{ I put in a LOT of vents on the ears expecially on pointy ears. I don't have the money to shell out for a full out vaccum thing, but someone, twigling maybe? said something about a pressure pot? Does anyone know about that? I'll try the talc thing too, that might be helpful.

 

I think Kaye has been talking about it in another thread, since she uses a setup with a pressure pot; but to run a pressure pot you also need an air compressor (also handy for airbrushing).

As for using an electric toothbrush or a washing machine on spin cycle, I guess any vibrating device could do the trick

 

I've been told about a table that vibrates, meant for pouring molds. Now, the lady I talked to said that she couldn't use the tables herself because she poured concrete, but there are tables that shake and can hold up a bunch of weight when dealing with resin. She said they're called Shaker Tables, but I haven't seen one. It might be worthwhile to do a little hunting. ^_^

EDIT: How to Build a Shake Table

Hope this helps!

 

Wow thanks Keanna, that's really helpful! My boyfriend is a real genius at things like that so I could get him to make one up for me.

 

Has anyone considered using a cell phone on vibrate?

 

Great tips! I'll have to try all this stuff when I begin casting things....*nervous but wants to try* Thanks! ^^ I should have no problem finding things that vibrate a lot for that X33; *LOL*