DIY Latex Rock Molds and Sculptamold

[BigDaddy]

Guess what I found in my backyard?

It is a piece of coal.  Every side is a potential rock mold.  Woo hoo.  I don't live where coal would be naturally found, it is litter, but a whole lot more useful the the scraps of concrete I find

[mlehman]

With a DIY mold, I would definitely use some sort of release. Its been some time, but I recall the disahwashing soap mist seemed to work OK and definitely easier to keep it from getting messy than the oily ones.

Keep at the Sculptamold and don't be afraid to experiment with it. Sounds like you know what too wet is now. There really is no "bad" mix depending on what the goal is, but too wet is close. Go drier and it will only get better Unlike plaster, there is no ideal ratio of H2O to the mix. Mix it according to the working conditions you need. For a mold, drier than what you seem to have ended up with should work better. Sculptamold will hold detail nearly as well as plaster once you get everything dialed in.

[BigDaddy]

I used sculptamold for the first time.   I did not measure and it was a bit runny and took longer than advertised to dry.  MRVP removed their mold from their Canadian Canyons sculptamold, way earlier than I would have with hydrocal, so I did what they did.  Detail might have suffered a little on the left side, by doing so.  It is not nearly as heavy as plaster and maybe not as hard, but good enough.

I did not mix in enough craft paint to color it as darkly as I wanted, but this was the reason to do a practice piece, before trying it out on the layout.

Good judgement comes from making bad choices and for my next mistake, I did not start with a black wash.  The deepest crevices did not want to take any color by brushing Walmart craft paints.  By wetting the brush did wash color into the area but put more color on the highlights than I thought necessary.

I added some highlights by dry brushing with white and turned the piece upside down and added some shadows with the same technique and black.

My last mistake was thinking I knew how to mix a rust color with the paints I had.  You will see a trace of red at the top right upper corner.  I hid the worst of it with brown.

This is the same piece and the same orientation as above.  I don't intend have a single casting be as multicolored as this.  This was purely my test canvas.  However if you look at pictures of Sidleing Hill, there is a lot of color out there

http://www.geologyin.com/2014/05/sideling-hill.html

[BigDaddy]

I went with latex.  I used PAM and I didn't use PAM.  I see no difference.  The latex peels offs the same with both.

Time consuming?  I'm retired, so nobody is paying me if I sit or work.  In a week I made 4 molds.  Indoors and airconditioning the latex takes a while to dry.  I considered the oven, and even tried it once, but I didn't want to melt the latex or crack the rock.

The rock really heats up outside in the sun.  When a thunderstorm rolls in, if the latex hasn't dried, it turns white, but doesn't seem to be damaged and eventually dries out.  If you have no other distractions, you can easily crank out 1 mold/day

They are not easy to take a picture with a cell phone and get it in focus.

 You can see the cross hatch of 4x4 gauze, that is translucent and not visible as part of the mold

 

 

 

[BigDaddy]

I found this older thread which discusses latex vs silicon.

http://cs.trains.com/mrr/f/11/t/168745.aspx

I bought this rock at a bonsai show, years ago.  When you are good you have a tree and top and the roots running down the side of the rock.  I never got that good.

There are 20 differerent potential molds in this rock.  I have seen Bragdon molds, or the casting from them, and they are excellent.

I bought some liquid latex from Modeltrainstuff.  Since I used that before, that's what I will go with.  Looked at a couple youtube videos.  Dave Frary used some "wet water"  Some other guy used nothing at all.

[MisterBeasley]

I've never used silicone for casting.  For Hydrocal castings, I use Latex rubber molds and spray then lightly with a bit of dishwashing liquid from a sprayer.

But, if you want a very lightweight casting, take a look a Bragdon Foam casting, www.bragdonent.com.  It does have a learning curve and takes some work to get that first casting, but the results are very nice and the surface details of the casting are excellent.

[hon30critter]

j. c.

i use pam

When I first read it, I thought that j.c. said "spam"!(as in the oft reviled canned meat product). I told myself that, OK, Spam is greasy enough to release anything from anything, but spreading 'Spam' on a rock mold must be a very messy process!!!

Sorry j.c. Couldn't resist sharing my mind fart!

I promise to make good use of your 'pam' recommendation when it comes time for my club to start making rock molds for the new layout.

Dave

[gmpullman]

BigDaddy

Thanks JC, but I was asking about release compound

j. c.

i use pam

https://www.pamcookingspray.com/products

I think j.c. uses Pam.

Hope that helps, Ed

[j. c.]

o #2 diesel is what i used.

[RR_Mel]

Henry

 

I’ve been using Ease Release 200 for about 7 years for silicon mold making and it does very well.

 

http://www.mann-release.com/erelese2.htm

 

It’s a bit pricy but it goes a long way.  I do a lot of mold and casting making and the can feels at least ¾ full after 7 years.  I bought it off eBay. I use it for Resin casting too.

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[BigDaddy]

Thanks JC, but I was asking about release compound when making the silicon mold itself. 

[j. c.]

i use pam , as far as weight, coat the inside of the mold with pure hydrocal , then after its partly set fill center with hydrocal mixed with ground up bead board cuts the weight about in about half . think thats what hydracal light is . or you could fill it with any plaster mix.

[BigDaddy]

Edit  Title change to reflect what I actually did.  I asked about silicon, but ended up using old fashioned woodland scenics latex. 

More than 30 years ago I made my own silicon latex rock mold castings.  It worked very well with hydrocal.  The recent MRVP Canadian Canyon series showed them using molds with sculptamold.

I can't remember if I used any mold release when I cast my molds.  Do I need any?

I see silicon on ebay for making facial masks, is that what people use now adays?

I imagine detail would be better with hydrocal, which is what I used to use, but I'm planning to move and I don't want the weight or the brittle plaster.

While I am asking, sculptamold comes in 3 and 4 pound packages.  The extra pound costs, 50-69% more for 33% more.  I can't quite grasp that concept.