I bought several plaster portals and stone walls from Woodland Scenics and intend to use them as masters for making latex rubber molds. Is there any special prep I must do to the plaster portals/walls before I apply the latex rubber?
cowman One thing I will suggest is that after a couple of layers of latex, cover a layer, while still wet, with some fiberglass tape (wallboard tape), then give it another layer or two. It makes the mold much stronger and it will last a lot longer. Good luck,
One thing I will suggest is that after a couple of layers of latex, cover a layer, while still wet, with some fiberglass tape (wallboard tape), then give it another layer or two. It makes the mold much stronger and it will last a lot longer. Good luck,
I have used used dryer sheets. Due to the finer mesh they are a little more difficult to get soaked with the latex but seem to have resulted in comparable results. I have used my 'dryer sheets supported molds' many times without a problem.
This is a timely and interesting subject for me as I am contemplating trying to mold some interesting rocks my daughter collected for me. Can anyone please give me a brand name or two. Also is it available at Michaels? My two nearest hobby shops don't carry anything like this. As always thanks.
Brent
"All of the world's problems are the result of the difference between how we think and how the world works."
The pieces I have now are brand new raw plaster. They have never been painted or stained. I didn't know if the latex rubber would react with the plaster, i.e. soften it which would destroy much of the details.
Mark:
The raw plaster of the master will present a problem in that it will adhere strongly to the rubber in places with the result that you will risk either tearing the rubber or damaging the master when you try to remove the mold. I found that sealing the plaster master a couple of coats of Minwax Polyacrylic varnish gave a nice surface and the rubber molds separated nicely. I sprayed the finished mold with a little wet water (water plus a drop or 2 of liquid dish detergent) before adding the plaster and the finished castings separated nicely.
Joe
Brent,
The only brand I know of is Woodland Scenics "Latex Rubber" it's number is C1204. Since I have no Michaels or the like around I am not sure what you should look for. Try asking for Latex Rubber. If that doesn't work ask your LHS to add it to his next order. They are usually happy to do this, they can special order, but that usually costs more and for that you'd probably do better to place an order with a mailorder or online store.
Good luck,
Bob W [FL]
If it ain't broke.... Fix it till it is !
I was just looking at the Micro Mark cataogue, which shows a number of different one and two part molding rubber compounds. The current catalogue pages 26 and 27 show a considerable number of items for making molds and castings, while on page 76 they list a Mold Maker Liquid Latex rubber, a single component item, 32 ounces for 22.85.
An article on molding parts I just scanned into a JPEG file show the author spraying the master with spray paint to seal the surface and make striping it from the mold easier.
It's been a while since I read articles in MRR and RMC about making rock molds, but I seem to recal the rocks may have been sprayed with water or "Wet Water" (water with a couple drops of liquid soap added.
If you get the liquid rubber, just get a couple random rocks of little interest and expirement.
Latex? yeah~ The stuff has been around for quite some time. I have had decades of using it. Everything this thread has said is true.
Finding it in a fairly large quantity can be hard. I could not longer find it in a hardware store.. or even a craft store. And if I found it, it was usually too small of a portion to do any real mold making. I found latex on ebay, and it was fairly cheap.
Latex has a few drawbacks. One.. never leave the latex out in the sun. Two, it takes time to make a mold. Lots and lots of coats. If done correctly if it fairly flexable but if you add the cloth (and you should).. fiberglass cloth or the wall tape it makes the mold stiffer. The more difficult the mold.. the harder it is to release after pouring. And if you have stiff latex molds.. trying to pull the plaster out of the mold can cause some damage. But then again, I don't use everday plaster, I use dental plaster. Its finer than most.. and usually a whole lot stronger.
Now on the other hand. Silicone is the 21st century of choice. Latex is a bit of 'old school'. Silicone is very expensive but tops the others in many ways.
One Silicone is extremely flexible. Two, is easy... just pour and let it dry.. you're good to go.. the next day. Three. silicone can take very high temps for pouring.. in case you choose to pour metal in the mold. With latex, plan on a week, especially if you don't have the time.. to apply one coat.. after the next .. and so on.
So, latex or silicone can be bought off ebay. AS far as learning how to make molds.. its on the internet.. its fairly easy.. but time consuming. Try YOUTUBE also, I have found so much "How to do stuff" on youtube, I'm sure there is something. My advice to you, if you don't have to worry about money.. as compared to time... go with silicone. I will try to follow up with my latex molds.. but I will also show you the silicone now~
This is silicone, bought off ebay. Its a 50/50 mix.. the liquid is very thick. In terms of mixing this stuff,.. well its so thick.. you have to turn the jugs upside down.. back and forth for a couple of hours. If not.. you might get a blemish in the mold.
As you can see the mold has its blemish... but its soft .. softer than the softest rubber eraser kids have in schools. So as far as mold making.. with silicone. Find the part you need.. glue it lightly down to the paper, build a wooden frame around it.. and pour. The silicone separates from the initial part fairly easy. And thus, you have a lasting mold.. one you can use over and over. In the upper right hand corner, is a bashed tunnel portal, I didn't like the thin stuff available.. so I made it thicker.. and made a mold. The lightly painted version, was done for some friends that wanted to see the actual mold and the aspects of making one.
I hope this helps. But in the long run, I'd guess you'll go the route of latex.. but half way through, you'll be wishing you would have spent the money on silicone.
Just one man's opinion. Take care.. good luck.. Blazzin aka Keith
randythawkinsI have used used dryer sheets. Due to the finer mesh they are a little more difficult to get soaked with the latex but seem to have resulted in comparable results. I have used my 'dryer sheets supported molds' many times without a problem.
That's a very clever suggestion-- thanks! I'm going to remember that one.
I wonder how well cheese-cloth would work? I've not tried it myself but the weave is looser than the dryer sheets and the fabric is easily available.
John
JoeinPA Mark:The raw plaster of the master will present a problem in that it will adhere strongly to the rubber in places with the result that you will risk either tearing the rubber or damaging the master when you try to remove the mold. I found that sealing the plaster master a couple of coats of Minwax Polyacrylic varnish gave a nice surface and the rubber molds separated nicely. I sprayed the finished mold with a little wet water (water plus a drop or 2 of liquid dish detergent) before adding the plaster and the finished castings separated nicely.Joe
More good information. This is a very useful and informative thread-- thanks guys! I'm learning a lot just reading along.
Blazzin This is silicone, bought off ebay. Its a 50/50 mix.. the liquid is very thick.
A 50/50 mix of what?
EDIT: Nevermind, I re-read it and figured it out-- a 50/50 mix of the parts 'A' and 'B' resin & catalyst.
jwhittenThat's a very clever suggestion-- thanks! I'm going to remember that one.I wonder how well cheese-cloth would work? I've not tried it myself but the weave is looser than the dryer sheets and the fabric is easily available.John
It would probably work ok. I can't say that working with the dryer sheets was something that thrilled me but I had plenty and it was worth a try and I am content with the results (e.g. not had any problems) so I would use it again.
Give the cheese cloth a try and post your results. I, along with others I am sure, would like to know how it worked.
Randy
jwhitten randythawkins I have used used dryer sheets. Due to the finer mesh they are a little more difficult to get soaked with the latex but seem to have resulted in comparable results. I have used my 'dryer sheets supported molds' many times without a problem. That's a very clever suggestion-- thanks! I'm going to remember that one. I wonder how well cheese-cloth would work? I've not tried it myself but the weave is looser than the dryer sheets and the fabric is easily available. John
randythawkins I have used used dryer sheets. Due to the finer mesh they are a little more difficult to get soaked with the latex but seem to have resulted in comparable results. I have used my 'dryer sheets supported molds' many times without a problem.
You can also try Handi-Wipes. Very strong with a loose weave that soaks into the latex. Makes the mold stronger and last for many castings.
dgwinupjwhitten randythawkins I have used used dryer sheets. Due to the finer mesh they are a little more difficult to get soaked with the latex but seem to have resulted in comparable results. I have used my 'dryer sheets supported molds' many times without a problem. That's a very clever suggestion-- thanks! I'm going to remember that one. I wonder how well cheese-cloth would work? I've not tried it myself but the weave is looser than the dryer sheets and the fabric is easily available. John You can also try Handi-Wipes. Very strong with a loose weave that soaks into the latex. Makes the mold stronger and last for many castings.
It just goes to show that with a little creative thought not EVERYTHING needed has to be purchased specifically for a task...if you look around enough you can find free substitutes that can be re-purposed for our tasks.
I made up my own latex rubber molds of the WS portals with WS latex. I brushed the castings lightly to remove the dust, but otherwised I didn't treat them at all. It took several coats of latex to create the mold. The hydrocal castings I made with the mold came out very well, with plenty of detail.
Remember to cover the sides with latex as well as the face. You will need some depth to your mold to hold the plaster, so the molds need side walls.
It takes an iron man to play with a toy iron horse.
Why bother making molds looking like everyone else's or possibly infringe on someone's property rights? Fifty years ago I made a multitude of hand-sized rock molds from a stone retaining wall at my parents' home. Wash the selected surface with water and paint brush. Apply two or three layers of liquid rubber (let it set between layers), and before the last of these coats set, apply some cotton gauze. Then apply a couple more layers of rubber. Once set, gently peel to remove. I still have these molds.
My molds are essentially flat. After pouring about a quarter-inch of plaster on the mold, the mold and plaster would be applied to the landform surface after the plaster had set just enough so it wouldn't run off the mold. Remove the mold once the plaster has firmly set.
Mark
markpierceWhy bother making molds looking like everyone else's or possibly infringe on someone's property rights? Fifty years ago I made a multitude of hand-sized rock molds from a stone retaining wall at my parents' home. Wash the selected surface with water and paint brush. Apply two or three layers of liquid rubber (let it set between layers), and before the last of these coats set, apply some cotton gauze. Then apply a couple more layers of rubber. Once set, gently peel to remove. I still have these molds.
Something like this?
http://justtrains.railfan.net/Model_Layouts_CVRR_RockMolds_pg1.html
Pam cooking spray works.
One thing to remember about this stuff is that it does freeze and that apparently will destroy some of its properties. If it's shipped in the winter you can't guarantee it isn't stuck in a trailer or something in sub freezing weather. My LHS won't order it in the winter for this reason.
Anyone else have experience with this?
A number of years ago I made some silicone rubber rock molds off large lumps of coal. The surface of the coal lumps looked like miniature rock faces. I don't know where you could find large coal lumps now since most coal now comes as small lump stoker coal. In any case, when I made the molds I painted 2-3 layers of the mold material on the surface of the coal lumps. I think I may have sprayed the surface of the coal lumps with wet water before I started to apply the mold material. While the mold material was still wet, I embedded pieces of cheese cloth into the mold material and then added several more layers of the mold material to completely encase the cheese cloth. When the mold material was completely set, I peeled off the molds. I dip the molds in wet water before adding the plaster. I made plaster casts from each of the molds. I numbered each of the castings and the mold from which they were made so I can better visualize what each mold will produce. The cheese cloth can be found in the dairy section of your supermarket. Actually it's usually found in the paint section of the big box stores.
I've read about people maintaining the shape of their rock molds during the casting process by supporting them in a bed of packing peanuts. Think I've seen this in some of the MR How-To videos.
Bob
You said "if you don't put on 4 or 5 coats of acrylic on the masters". Do you mean you put 4 or 5 coats on the master?
Hello Kieth,
Thanks for the info,I purchased some 2 part mix from Aero Marine on your advise and i'm dying to try it out.
While its being shipped......Is there any other items such as mold release that i should have on hand before I try the process. Do you use styrene as a base to glue your part on?
Thank you in advance,
Hogwire
markpierceWhy bother making molds looking like everyone else's or possibly infringe on someone's property rights?
The Woodland Scenics portals are about an inch thick. They're also wider and taller than I wanted. So, by making a mold and then casting a copy, I was able to make a thinner, narrower version that fit perfectly.
I also created molds for casting the walls and platforms of my subway stations. The originals were styrene sheets with square patterns on them. For the platforms, I just think that a Hydrocal casting takes paint better and looks more realistic than trying to paint and weather plastic to look like concrete. For the tile walls, I can curve and shape the castings by bending the mold around a form after the Hydrocal sets up, but before it hardens completely.
Hogwire, ah no. There is no prep for the silicone. Well I've never used it. I was looking for some old portal I bought to show you .. it came broken.. glued it.. and siliconed it. As of now, I can't seem to find it. If I remember correctly the master had a very light blue tint left over on it. Not enough to clean.. and the remnant of the silicone was nil. Enough to paint it.. without any concern. Although I did not paint the master. Its around here .. somewhere. But since you asked the question.. and directed it towards me personally.. well I shall give you one demonstration.
This is important.
You have to mix the stuff up really good before pouring. If you don't, you might end up with a blemish. SO~ .. turn each jub upside down.. and then back again. This stuff is so thick.. you have to do it.. for about 2 hours. Well if you don't, you run the risk of a blemish.. as last shown in previous pics. Although, I've tried to figure out why I did end up with a blemish.. IMPORTANT> If you mix the silicone in a cup.. paper styrofoam cup.. .. heck pour the mix into one other cup.. I don't know.. but I would have guessed.. when I had scraped off the all the remaining silicone.. from the side of the cup, well the stuff sticking to the side of the cup.. WAS NOT properly mixed... even though all the other stuff was mixed. So, don't scrap off the remnants of silicone sticking to the side of the cup. That is why I say mix in a second cup.. then scrape off the remnants.. of the first cup, and then mix that stuff up with the second cup. If you think thats a bit much.. well.. the stuff is expensive.. so you do want to use evey last drop of the stuff.
Ok.. since that probably doesn't make sense.. here's what I am going to do. I shall use a box.. an old checkbook box.. place the masters inside.. lightly glue it with milk glue.. just enough around the edges of the master.. so as not to let in the silicone underneath... but also to hold it in place. Afterwards.. a lightly glued master with milk glue comes up fairly easy with water. Hlaf the time.. if glued lightly.. it peels off from the checkbook card box. The whole process is 1/10 the time of making a latex mold. The detail is fantastic.
Ok.. I will follow up with some pics.. then you decide. BTW.. don't look for an additional post.. I'll just add it here.. and just edit my post.
Well guys I am finding this thread really interesting, as I have all that is needed to make a silicone mould, but have yet to make the first mould, so all this advice is being read and will be used very soon.