posted
I need to cast some half spheres using tinted resin. A local plastics company sells molds but they only have about 3" diameter and I need them to be 1 3/4" to 2" diameter. Does anyone here in Lettervile know of somethig I can use for a mold thats about this size and shape and the resin won't attack? It doesn't have to be a perfect half sphere, just something close. I would prefer to buy these already made but I don't think I'm going to get that lucky. I'm doing some non-sign related art projects and I keep picturing this shape tinted amber and some in dark green. I feel like that guy in, I think it was "Close encounters of the third kind" who was building the tower in his living room and didn't know why but he had to do it. A lot my projects get stated that way. I'll have to have my helper do this because if I smell that stuff I'll have a real bad day. I used to use it to patch surfboards so I know it eats styrofoam cups but not other types of plastic. Thanks
-------------------- Chuck Peterson Designs San Diego, CA Posts: 1052 | From: San Diego, CA USA | Registered: Nov 1998
| IP: Logged |
posted
Chuck, I remember seeing an article in an old magazine-I think, SignCraft about someone doing molds. I don't remember what issue. I'll try to find it.
-------------------- Laura Butler Vision Graphics & Sign 4479 Welch Rd Attica, Mi 48412 Posts: 2855 | From: Attica, Mi, USA | Registered: Nov 2000
| IP: Logged |
posted
How about egg shells Chuck - Sold cheap by the dozen.
-------------------- “Did you ever stop to think, and forget to start again?” -Winnie the Pooh & A.A. Milne
Kelly Thorson Kel-T-Grafix 801 Main St. Holdfast, SK S0G 2H0 ktg@sasktel.net Posts: 5496 | From: Penzance, Saskatchewan | Registered: May 2002
| IP: Logged |
posted
Make the mould yourself , it shouldnt take more than 20 minutes. Buy ANYTHING thats the diameter you need , embed 1/2 of it in plasticine (modling clay) at the bottom of a paper cup and buy a 2 part RTV (Room temperature vulcanising) silicon - you can get it just about anywhere , normally from places that sell casting resin. Mix it up , pour it in , wait for it to cure and then brak the cup and remove the ball and plasticene and voila , you have a mould. The life of the mould depends on the mould material and the resins , some resins are agressive and some less so. The Resin supply guys should be able to supply you with EVERYTHING you need to do this - it's not rocket science
-------------------- Rodney Gold Toker Bros Posts: 57 | From: South Africa | Registered: Aug 2003
| IP: Logged |
-------------------- Jimmy Chatham Chatham Signs 468 stark st Commerce, Ga 30529 Posts: 1766 | From: Commerce, GA, USA | Registered: Nov 1998
| IP: Logged |
posted
Hi Chuck... Francis Lestingi from NY is an expert on mold making, in my opinion...maybe he would have an answer. Love- JILL
-------------------- That is like a Mr. Potato Head with all the pieces in the wrong place. -Russ McMullin Posts: 8834 | From: Butler, PA, USA | Registered: Jan 2001
| IP: Logged |
posted
It's not rocket science, but it can be damm frustrating. There are some combinations that don't work. For instance, West Systems epoxy does not like silicone. We have used silicone release agents that prevented the West from kicking, making a gooey mess. (Letting the release agent dry thoroughly before pouring in the epoxy helped, but it still seemed to grunge up the mold). We have used release agents that were not 100% silicone - BIG NO-NO. Silicone lubricants will NOT work as a mold release.
The only acceptable results were using silicone for the mold itself, then no release agent is needed, and nothing so far has harmed our molds. Two part RVT is expensive though. Our source is SmoothOn http://www.smooth-on.com, but they're a little hard to deal with. They only sell through distributors, not direct from their web site. The problem with that is the distrubutors are only order takers. You have to know exactly what you want when you call. If you make a wrong choice the distributor cannot advise you or warn you. Believe me, the information I learned about molds was painful.
Still, I wonder if a 'caulking' variety silicone could be spread over an object to make an useable short-term mold. I'd never risk it over something I had put a lot of time into, but it might be worth experimenting on a simple shape like a sphere. Anyone done it? I'm sure you'd probably need a release agent cuz that kind of silicone is more of an adhesive till it's cured.
SONGPAINTER Original Sign Music by Sign People NOW AVAILABLE on CD and the proceeds go to Letterville's favorite charity! Click Here for Sound Clips! Posts: 1974 | From: Orleans, MA, Cape Cod, USA | Registered: Nov 1998
| IP: Logged |
posted
When I used to do this. I would make a wood plug (usually on a lathe) then cast a negative, depending on the complexity in halves or the whole thing then cut it, then you have your mold! Depending on the casting material, you get the appropriate release, I think silicone spray worked well, but doing a transparent casting is a lttle trickier
-------------------- Rick Chavez Hemet, CA Posts: 1538 | From: Hemet,CA U.S.A. | Registered: Jun 2001
| IP: Logged |
posted
Joe, I buy from smooth-on all the time, straight from their website! Ya must not have been there for a while, I've been buying casting resins and mold rubbers direct for about a year now.
Chuck, ya know those little candy and toy vending machines you see at stores? the ones where they have the toys in the clear containers? those containers might work for ya.
For about $50, you can get a silicone mold kit (enough to make a few small molds) and a kit (about one quart) of low-odor casting resin (urethane) and some tints from smooth-on.
-------------------- "If I share all my wisdom I won't have any left for myself."
Mike Pipes stickerpimp.com Lake Havasu, AZ mike@stickerpimp.com Posts: 8746 | From: Lake Havasu, AZ USA | Registered: Jun 2000
| IP: Logged |
SONGPAINTER Original Sign Music by Sign People NOW AVAILABLE on CD and the proceeds go to Letterville's favorite charity! Click Here for Sound Clips! Posts: 1974 | From: Orleans, MA, Cape Cod, USA | Registered: Nov 1998
| IP: Logged |
![[Wink]](wink.gif)
Printer-friendly view of this topic