Mould making using resin casting

[Outland (Unregistered Guest)]

Hi All
I am looking for information on mould making
what i want to know is
Can i use pink foam from Home depot to cut a mould into like welcome sign or the like pour casting resin into it
what i need to know is will the resin affect the foam? will it be easy to drop the resin casting out of the mould so i can reuse it?
Has anyone tried this?

Thanks

[Brady Watson]

Outland,
I wouldn't advise doing that...for no other reason than it won't work, the finish will be terrible if you could remove the casting from the foam. It is possible to cast resin into a foam cavity and then melt the foam away with acetone. This is both messy and barbaric to say the least.

I would recommend carving a male model in pink foam and then sealing it with several coats of shellac. Then make a molding box and pour silicone rubber over the model. After this is cured, remove the foam and you are ready to do multiple castings of plastic resin. The Si mold will last a long time. A foam one will just waste your money and time.

-Brady

[steve minuskin (Unregistered Guest)]

Brady is on the right track. However, the Silicone will have to be degassed in a vacuum chamber in order to remove the air bubbles. Any bubbles left in the surface of the mold will be reproduced in the finished part. The last time I purchased Silicone it cost approx. $250.00 per gallon. Currently I make molds from Smoothon urethane 1515. This does not need degassing and can be demolded in 20 minutes, compared to 24 hours for Silicone. A soft Silicone mold will need a hard shell to maintain it’s shape. The shell can be made from fibre glass or plaster, depending on size.

You will also have to make sure your master form is PERFECT. A good quality mold will reproduce every tiny brush stroke or tool mark you leave on the surface.

[billp]

outland, pass along your e-mail address and I'll send you a list of web pages I handed out at the last N.J. Camp Shopbot which deal with mold making., Regards, Bill P.

[artisan]

Outland, there are basically two types of resin...epoxy based and polyester based. The epoxy based resins will NOT harm the foam. I own a theming and sign company and we do this sort of thing for small production pieces. You will need to add a step. Cut your original from foam. Sand your foam, coat it with minwax polycrylic, zinnser white shellac or even kilz, coat it with a release agent and then pour a cheap plaster mold around it. This works very well. If you cut the original on your shopbot, you can be sure there will be no undercuts. Brush the mold with a release agent...murphy's oil soap works well...and your resin casting will release easily after cooling down. Good Luck....D

[jay]

Bill, could you post the list of web pages here on the forum. I would love a copy of the pages as I am sure others would as well, Jay

[billp]

Jay,
Here you go ;
(If anyone comes across 'dead links"please let me/us know), Thanks

Mold making
(tutorials/info/materials)

http://www.mouldmaking.freeserve.co.uk/indexlinks.html
http://www.polytek.com
http://www.sculptnouveau.com
http://www.smoothon.com/
http://www.sculpture.org
http://www.sculpt.com
http://www.remet.com
http://www.artmetal.com
http://www.ball-consulting-ltd.com
http://www.plastermaster.com
http://www.aluminite.com
http://www.igestoolbox.com
http://www.freemansupply.com
http://www.reynoldsam.com
http://www.garlic.com/~blufrogg/dolls/mold.htm
http://www.rubbermoldcompounds.com/
http://www.alpineimport.com
http://www.quantumsilicones.com
http://www.lumicast.com/
http://www.castcraft.com/
http://www.cementex.com/
http://www.mann-release.com/
http://www.culinart.net/silicone.html
http://www.mikethealchemist.com/
http://www.apcmg.com/moldmake.htm
http://www.artmolds.com/alginate_moldgel.htm
http://www.nevolution.org/tutorial.php
http://www.kitcar.ca/links/links.php?cat=29
http://www.geocities.com/brothaj311/megohowto.html
http://www.engr.udayton.edu/faculty/rkashani/plastics/tutorial.html
http://www.boalsdesign.com/Tutorials/Latex.htm
http://www.forestinaflash.com/index.asp?choice=3
http://www.southerngfx.co.uk/general/reviews/rhino2/review.htm
http://www.nextcraft.com/rcdesignandbuilding.html
http://www.geocities.com/angelsunawares/Kwesi3.html

[jay]

Wow!
Thanks Bill, I know what I will be doing for the next couple of hours.

[Brady Watson]

Steve,
I've had very good luck with the PolyTek line of silicones and RTV rubbers. I also use their casting resin as well with great results. It isn't normally necessary to degass the silicone depending upon how you pour it and what resin you are putting into it. I have several Si molds with perfect surface finishes that were not degassed. If you have a vac pump, then by all means do it. If you are casting clear, then yes you need to vac degas it because you vac degass the clear resin.

Yes Si is expensive...and regular RTV rubber will work at a lower cost. Tin Si instead of Platinum Si is also a good choice and isn't affected by standard resins.

I attended PolyTek's mold making seminar last year and one trick to avoid bubbles (in addition to properly pouring the rubber!) is to spray the back of the mold right after you pour it with their 2300 Silicone spray. It breaks the surface tension and you can watch the bubble breaking the surface.

-Brady

[Mayo]

The aluminite link is not dead but it doesn't seem to be related to mold making.

[Brady Watson]

Probably because it is alumalite...not aluminite.

www.alumilite.com (http://www.alumilite.com)

[garbob]

WOW,

Thanks Bill!

[jamon61@hotmail.com]

Two more:

http://www.synair.com/
http://www.industrialpolymers.com/

I have used Synair products for 6 years. I'm about to order several resins from Industrial Polymers Corp., to evaluated. I make molds for a lost wax foundry.

John

[COESTERF001@hawaii.rr.com]

Aloha Everyone! Does anyone know what type of resin is used to replicate lava. I want to make castings that look like CoCo Joes,Poly-art and HIP items. They are flat black and said to be made with lava. The older pieces are heavier than the newer ones. mahalo, Freddie

[Brady Watson]

Freddie,
There are a few ways that you can do it. First thing that comes to mind is to make your 2 pc mold out of silicone. Leave a hole to fill with resin and a cork to fit the hole.

I would recommend doing a slush casting using EasyFlo 120. It cures quickly and is made for roto & slush casting because it gradually kicks instead of instantly 'freezing' like EasyFlo 60.

Mix up a batch of PolyTek EasyFlo 120. Let's say you make 8oz of it. Add 8Oz of pumice powder to it or ash or whatever you have that is powdered lava...I imagine that shouldn't be too dificult in Hawaii. Pour it into the mold and rotate it in all directions with your hands. In about 5 minutes it will kick off and you will have your CoCo Joe. You will have many scrap pieces until you master the technique of slush casting.

You can also mix up a smaller batch just to coat the face of the mold, and then back it up with plaster, or any other substrate you want to give you weight. PolyTek 15X comes to mind here.

-Brady

[beacon14]

I did some pieces for a movie set once where the walls of this large room were made to look like rock, very similar to a lava look. They lined the walls with styrofoam sheets, then sprayed lacquer thinner all over the foam with hand spray bottles (like what glass cleaner comes from). The thinner ate away the foam, leaving a surface that looked just like porous rock after it was painted.
Not sure if this will help, but it brought back some memories.