Refractory Mold

Here is a pic of the three sections of firebrick. They were very difficult to remove from the mold even though I tried all of the pointers offered here namely wax on one,oil on another and axle grease on the third [that's the one that is dark on top. I had to chisel them out and rough the edges. Amazing that they did not break.They are dimensionally right on and a bit of work with a caulking tube of refractory will seal the top and joints. They weigh 9 pounds two ounces each so the 40# bag will easily make 4 of them. any further suggestions regarding mold release methods would be helpful.Possibly this cement expands when it cures?? Mike

stovepipemike wrote:Here is a pic of the three sections of firebrick. They were very difficult to remove from the mold even though I tried all of the pointers offered here namely wax on one,oil on another and axle grease on the third [that's the one that is dark on top. I had to chisel them out and rough the edges. Amazing that they did not break.They are dimensionally right on and a bit of work with a caulking tube of refractory will seal the top and joints. They weigh 9 pounds two ounces each so the 40# bag will easily make 4 of them. any further suggestions regarding mold release methods would be helpful.Possibly this cement expands when it cures?? Mike

Make the sides of the mold removable also, maybe held together with allthread and nuts?

Good thinking!! Now that is an idea, to add to it I would only have to bolt one side and leave the other welded as a standard to check for alignment and dimension. ,Mike

I had very good results using the Supermarket's house brand of vegetable based cooking spray - their equivalent to "PAM" brand cooking spray, but much less expensive. Did not interfere with the cure of the refractory, yet it was easy to wash off the mold parts.

I used a small painter's brush to spread it evenly.

Paul

I have used plastic shopping bags , cut open and laid out smooth in the mold. works good in the old wooden molds I have for cook stoves
Wilson

stovepipemike wrote:Here is a pic of the three sections of firebrick. They were very difficult to remove from the mold even though I tried all of the pointers offered here namely wax on one,oil on another and axle grease on the third [that's the one that is dark on top. I had to chisel them out and rough the edges. Amazing that they did not break.They are dimensionally right on and a bit of work with a caulking tube of refractory will seal the top and joints. They weigh 9 pounds two ounces each so the 40# bag will easily make 4 of them. any further suggestions regarding mold release methods would be helpful.Possibly this cement expands when it cures?? Mike

Mike... I cant even tell you how impressed I am at your efforts & time you must have put into this... I can tell you oil (like motor oil) seems to work best. The reason for the tightness coming out is the sides of the mold at the point of where the cement contacts them (if these side were a "hair" inward (which can occur from fabrication/welding) it will make the pull very hard!!! if these sides were a "hair" outward it would make the pull very easy (and as long as its a very slight outward, it would have no ill effect on anything).... I hope that helps my friend... amazing JOB!!!

Automotive paste wax coating works well.

Paraffin? What is used as a mold release for fiberglass?

Vegetable cooking spray worked very well as a mold release with the castable refractory fire bricks I made for my Glenwood #6. Does not affect the cure, or strength of the refractory.

Sprayed it on and then brushed it out to make sure all surfaces were evenly coated. Needs to be recoated for each casting.

Also, ridged molds usually have removable sides to make cast part extraction easier and less risk of damaging the cast part, or the mold, by trying to pry it out.

Or, as is often used commercially, a flexible mold like mold-making polyurethane within a box to support it - which is what I did. The mold can "give" to allow extraction without damage to box, mold, or cast parts. Works like latex molds but the polyurethane last far longer- especially working with concrete (refractory).

Paul