Why do I need a chisel to get my Aluminite blanks out of the molds?

[FGarbrecht]

Started casting aluminite clear slow in HDPE molds as well as PVC pipes. I use Stoner mold release on the molds. The blanks come out very nice but very hard to get out of the molds -- I've had to pry them out of the square molds with a chisel, and for the PVC I had to turn the PVC off on the lathe. What am I doing wrong? I thought I was being generous with the mold release but maybe I need more?

 

[1080Wayne]

Doubt if you are doing anything wrong . I`ve never used the slow , but assume it behaves similar to the Clear in that it doesn`t shrink as it cures . Your molds are unforgiving in the sense that they are stiff and not flexible . I just use small single layer cardboard boxes , reinforced with duct tape to prevent leaks , if I want squareish blanks , but generally use tubes ranging from large vitamin bottle size down to caulking tube , toilet paper roll or smaller , depending on what I`m casting . Disposable is the common factor . No mold release required .

 

[Kenny Durrant]

I'm familiar with the brand Stoner and used a spray several years ago but that's about all I remember. I used the brush on wax based release and it worked well but if you didn't keep the molds perfectly clean you would get wax flakes in your casts. I started using the spray silicone release and it works great. The cast come out crystal clear as well. I spray the release in the mold and on the silicone plugs as well. I have a dedicated brush that I use to even the spray on the molds and plugs after spraying. The blanks come right out with no problems. When a blank is tight or hard to remove it because the mold has tool marks or ridges that help hold the blank in place because of no shrinkage. I never used PVC only HDPE and Delrin. Both of those act the same as far as my demolding. The specific release I use is a Smooth-On Universal Mold Release Spay.

 

[MRDucks2]

Not sure what difference it makes but Stoner makes different flavor mold releases. I see both epoxy and urethane versions in my shop.

I cast in hope molds made from textured cutting boards and haven't had any issues with it releasing, but it does require a sharp rap on the bench or with a mallet to get it break loose.

Haven't yet tried the pvc I have cut.


Sent from my iPhone using Penturners.org mobile app

 

[TattooedTurner]

I've never had trouble getting Alumilite out of pvc. My guess is your Stoner isn't the one for urethane resin.

 

[bmachin]

If you're willing to put in the effort Curtis Seebeck at Turntex has plans for a flat mold made from poly cutting board which is screwed together. The advantage is that you can remove one side of the mold to remove the casting. Plans here:

Making Casting Molds from Cutting Boards

Making Casting Molds from Cutting Boards

www.turntex.com

Bill

 

[erichardson]

If I have stubborn PVC that refuses to release the blank, I have put it in my freezer for like 10-15 minutes and it pops right out. I do use Stoner Mold release, but every once in a while I have a stubborn one.

 

[howsitwork]

i used HDPE sheet to make my molds and screw together. the stoner works on them ok.

Have you checked for taper in your molds ? if the are even slightly tapered from base to top then your stuck fast but with screwed moulds you can ease apart. Never tried tubes but i intend to now but , at my current rate of production that may mean january 2020 .
the pine cone block shown needed four pourings but came loose no bother , stoner was used .