Casting Frustrations!!!

[Brandy]

I've been trying my hand at casting for about a year now and I always have the same problem. The wood (or whatever I'm casting) floats up enough to make the blank unusable and, when using a block mold it will be full when I place it in the pressure pot but when I remove it the level of the resin has dropped making the blanks too thin (but only on one end). Sometimes I find resin on the bottom of the pot and sometimes I don't. Where is it going?!

The pressure pot is level (I check it each time). I use PTown Stubbies blue molds and am wondering if I need to use a less flexible mold?

 

[PatrickR]

I don't use the silicone molds but in HDPE or coroplast I use a little hot melt glue to hold the wood down.
i have had resin get forced into soft, open grain, not stabilized wood before. If its not running out it has to be in the wood.

 

[MRDucks2]

I have glued wood in place, used rubber bands, used additional wood and placed another silicon mold over the top, etc. Wood floats, at least most of it does, so you have to be creative on how to get it to stay in place. Even oversizing pieces to get them lodged against mold sides. Also, if it floats it moves and if it moves it can move resin out of place.

 

[JohnU]

I'm guessing your attaching the air hose to the pressure tank while the valve is open? This creates a huge inlet of air all at one to me which will blow the resin out of your mold, inside the tank. Always close the valve, then connect the air hose, then open it slightly to pressurize. Also, depending on what resin your using, some, like polyresin, shrink while curing, which could account for low resin in the mold. Also, if there's a lot of air bubbles in your mixed resin, the level of resin will drop some as the air leaves the resin. I would suggest getting a deeper mold so you can pour extra in each pour to get the thickness you want. Good luck!

 

[Brandy]

I'm guessing your attaching the air hose to the pressure tank while the valve is open? This creates a huge inlet of air all at one to me which will blow the resin out of your mold, inside the tank. Always close the valve, then connect the air hose, then open it slightly to pressurize. Also, depending on what resin your using, some, like polyresin, shrink while curing, which could account for low resin in the mold. Also, if there's a lot of air bubbles in your mixed resin, the level of resin will drop some as the air leaves the resin. I would suggest getting a deeper mold so you can pour extra in each pour to get the thickness you want. Good luck!

I've had issues blowing the resin out before so I usually close the valve then open it after the air is attached. I hadn't thought of the shrinkage factor or the air. I do have a lot of bubbles. Thanks!

 

[howsitwork]

i found using bits of hdpe to hold the wood down into the mold works?
I put masking tape around the mould to hold the hdpe in place. Resin doesn't stick to the hdpe .