Casting q

[Hitogiri]

Got a few questions here I really need help with.

My main concern is air bubbles in the final cast.

1. How do you eliminate air bubbles if you do not have access to a vacuum forming or injection molding setup?

2. Why is resin viscosity(sp?) important?

3. How do you polish up something like resin? I would think buffing might be too abrasive but not sure.

 

[hydin]

1: low viscosity resin helps a lot, but being careful when you pour does wonders as well. if you can, get a slow set resin and it will give the resin time to degas and you come out with a pretty bubble free casting. not getting airbubbles on a solid (white) resin casting is pretty easy as well. warm the mold a bit before you pour, and dust the mold with talcum powder (non silica cornstarch kind). works like a charm. wont get the cast 100% bubble free, but it gets rid of surface bubbles.

2: the thicker the resin the more air it traps, and the more air it traps the bigger the bubbles, and the more awful the cast is.

3: if you mold something that is glossy (like plexiglass or something glass smooth), when you make that casting it will come out very smooth already. if you are using clear resin (or something colored but transparent, like a red rose or jewel), you can use future floor wax to get a nice "buff" shine. start out with about 400 grit sandpaper and work up towards a wet sand at 2000 grit, and you will have a mirror finish on whatever you are making.

as far as polishing white resin... i think thats more of a paint issue than a resin issue.

hope these help
chris

 

[Hitogiri]

So a low viscosity slow setting resin less likely to have air bubbles present on the surface.....can you suggest a good resin that is durable?

 

[SgtFang]

Dust your mold with baby powder before you pour- it breaks the surface tension and sucks the resin into every little nook and cranny.

-Sarge

 

[Bob Gaussington]

Pouring really high in a tthin stream helps, as well. It looks weird pouring from a couple feet up, but it really does help with the bubbles.

 

[Hitogiri]

Thanks guys. I'm gonna try and find a good resin and try it in the next few weeks.