glycerine
Member
For those of you that have used both a silicone type mold and a hard HDPE type mold, which do you prefer? What are the pros and cons of each. I know they can both be made easily, so does one have an advantage over the other?
Which mold?
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PTownSubbie
Member
What comes to mind first is that the HDPE mold probably has to have the sides removed so the blank can be taken out where the silicone pulls away from cast with no problems.
Not sure if that is what you were asking for though.........
Not sure if that is what you were asking for though.........
jocat54
Member
I have been using molds I made from cutting boards--it is a little bit of a PITA to get the blanks out but not that bad. At first I was taking a side off the mold but now I coax them out intact using a small pry bar (screwdriver) works pretty well. If you take a side off the mold then you have to apply silicone each time to seal it back.
John
John
MesquiteMan
Retired Head Moderator
I use cutting board molds and take one side off each time to get the blank out. I have never sealed any of the joints with silicone and do not have a problem. I do get a tiny bit of leaks occasionally but not enough to cause problems. Then again, I am using Alumilite and it sets fast enough that leaks are not an issue. I also attach the sides, then run it through my tablesaw to make sure everything is perfectly flush before attaching the ends.
glycerine
Member
Yes that's exactly what I mean.
glycerine
Member
Thanks for the info. Other than NewLondon's molds, it seems like most people who are making thier own are making them out of cutting boards or HDPE, so I was just wondering if there was an advantage over silicone. I was going to make some silicone molds, thinking it would be easier to get the blanks out. But also don't know that I could put silicone in the toaster if I need to aid the PR in curing...
dogcatcher
Member
I made my own molds using silicon and I will never go back to any of the other versions. In the past I had used PVC and the cutting board molds. I used the silicone mix and made the mold using PVC pipe. No waste and easy to unmold.
jason_r
Member
I have and use both. By far I prefer the rubber molds -both the ones
I've made and the ones I've bought.
Much easier to demold.
The HDPE (cutting board) ones aren't bad if casting PR since it
shrinks enough. Alumilite can be a real challenge to demold without
disassembling (or freezing- but I only use that on alumilite in steel pipe
molds)
Only drawbacks to rubber molds:
1) You want to support them to keep them flat- especially in
a PP where the bottom's not flat or you're stacking.
2) The rubber molds wear out (but so do HDPE ones).
I've made and the ones I've bought.
Much easier to demold.
The HDPE (cutting board) ones aren't bad if casting PR since it
shrinks enough. Alumilite can be a real challenge to demold without
disassembling (or freezing- but I only use that on alumilite in steel pipe
molds)
Only drawbacks to rubber molds:
1) You want to support them to keep them flat- especially in
a PP where the bottom's not flat or you're stacking.
2) The rubber molds wear out (but so do HDPE ones).
NewLondon88
Local Chapter Leader
That would depend on the particular silicone you use. The ones I'm using
are good to over 400 degrees (far higher than you'd ever want with PR) so
you shouldn't have any problem as long as you check the spec. sheet from
the manufacturer. Shoot me a PM if I can help.
LandfillLumber
Member
I use cutting board molds and have no issues with PR releasing from them just flip it over bang it on the table and its out.Now urethanes are a little more trouble as they do not shrink like PR,but still like Curtis says just remove one side(2-4 screws).I suggest attaching the molds to 3/4" plywood to keep them flat I have had blocks come out with a little curve to them until I help them flat against the 3/4" ply.Good Luck,Victor
workinforwood
Member
I use both types of molds equally. I would actually prefer to only use silicone molds, but nobody has one to suit my needs for a particular type of casting I do. The silicone is the fastest and guaranteed not to leak. Like Curtis, I use alumilite, and so with cutting board molds, if they do leak it is very minimal and not an issue, but you still have to unscrew one side of the mold which is a minor annoyance. The cutting boards do have the advantage of keeping the finished blank more square, as in the walls are less likely to push in...well they do push in a bit with cutting boards, but not as much as with silicone. I'm rather split 50/50 with the pro's and cons of each.