Making Miniatures

Gettin' the lead and makin' it pretty
thedugan
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Postby thedugan » Tue Oct 21, 2008 12:10 am

nathan wrote:Well, I gave the process a test. I used it on some model kit sprue I had because they had some really fine pressure pin lines and I wanted to see if it would pick them up. I tried the method above (straight silicone for the first layer) but I didn't like the process. It was a major pain to work with.

So I tried the tinned method. Much better. But too slow to cure. The post on that Myheap site said that using glycerin or paint with the thinner would make it lumpy and that it was counter productive. But I tried it anyway. I thinned down some silicone caulk with some camp fuel (naphtha white gas) and added glycerin and paint. It didn't turn lumpy at all. I painted it on (and it went on easily when thinned) and set the sprue chunk aside. It cured fast and normally. It didn't lump up or shrink or anything. Naphtha as a thinner and glycerin and paint as a catalyst work together just fine.


Cool! more tools for the toolbox, and another confirmation of technique. How much did you thin it? What were your proportions?

I found that diluting it with Mineral Spirits much would result in the mold curling up if the mold was thin in cross-section.

nathan wrote:My friend has some plaster blocks in which he carved a stone pattern that we wants to test it on, so I'm going to do that Saturday. Plaster is pretty porous, so I'm going to have to do some reading on how to properly seal it.


Watered down white glue/Elmers (PVA glue for the Brits out there) or shellac should do the trick.

nathan wrote:Oh, and the silicone replicated the detail just fine. It even picked up some pin indents that I couldn't see with my naked eye. I saw them when I looked through a magnifying lense and thought something was wrong with the mould and then grabbed the sprue and saw them on the sprue itself.


Excellent.

nathan wrote:I've always not bothered doing much more than the occasional conversion because I thought replicating what I made wouldn't be economical. But now... now there's scratch building to be done.


:)
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nathan
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Postby nathan » Tue Oct 21, 2008 1:23 am

thedugan wrote:Cool! more tools for the toolbox, and another confirmation of technique. How much did you thin it? What were your proportions?


3 parts silicone, 1 part naphtha based thinner. It was enough to make it paintable with easy but no more. One guy quoted on that myheap site says you could go 50/50 and it should still work. My thinking is to not thin it any more than necessary though.

I found that diluting it with Mineral Spirits much would result in the mold curling up if the mold was thin in cross-section.


Did you also add a catalyst? I also just painted the mixture onto some glass to see how thin I could get it and the 3:1 silicone/naphtha with paint as a catalyst didn't deform, even at the edges where it was thin enough to be translucent. I forgot about the mould release though and couldn't get it all off the glass (which is made from sand/silica, so silicone sticks to it). I'm going to get some cheap corrugated plastic "for sale" signs at the dollar store for future mould box use.

Watered down white glue/Elmers (PVA glue for the Brits out there) or shellac should do the trick.


We ended up postponing the trial mould making after it came to light that some of his pieces will require a two part mould. So we're going to need some non-sulfur clay for that process. It's going to be a challenge, combining brush on mould making with the techniques for making a pourable mould. I think we'll give the PVA a go. Vegetable oil spray seems to be working fine as a mould release agent off of the glass and sprue I've tested the silicone on so far.

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Postby jimbeau » Mon Oct 27, 2008 10:46 am

nathan wrote:Thought this might be pertinent:

http://www.taxidermy.net/forum/index.ph ... 157.0.html

Apparently using cheap silicone and polyester resin to make castings is a common practice among taxidermists. Not a bad little guide.


Well, I tried this too, here are the results.

I used silicone right out of the tube and a 1:1 mixture of Dawn dish-soap and water. I cast the part out of merlin's magic dental plaster.

I started with a very complex item that had deep undercuts and I have to say the results we more spectacular than I expected. I will be casting a bunch of these guys in the near future to test how long the mold lasts.

Image

nathan
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Postby nathan » Mon Oct 27, 2008 11:18 am

Amazing!!

I'm shocked it worked so well on a piece of lava rock. I would have thought the silicone would have torn and the mould rendered useless. That's amazing.

My thinking is that even if I get 5-10 casts out of a mould, for the cost and ease of getting the materials, that's worth it.

thedugan
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Postby thedugan » Mon Oct 27, 2008 3:05 pm

Wow, the details on that are pretty amazing.

I'm not really surprised that the mold worked, but I gotta wonder just how tough the Dental plaster stuff is, and how much it cost.

I'm not questioning that it worked, just whether or not it's the most cost-effective solution.

Got a link for the Merlin's Magic and a tutorial/testamonial about using it?
Becuz I'm da friggin' ART FAIRY - dats why!

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nathan
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Postby nathan » Mon Oct 27, 2008 4:23 pm

I've done a bit of casting (hirst arts moulds) with dental stone and it's quite strong. I had this crazy micro resin bubble reinforced stuff with like a 20,000 psi break strength. Bought it at a local dental supply place. Check your phone book and give them a call. Tell them you want to get some high psi (10,000+) dental stone. Expect to pay about a dollar per pound.

I could spike the 20,000 psi stuff I had on concrete and I'd only get corners chipping off the blocks on a single throw. Took a couple throws to make it shatter. Thin pieces though, broke far more easily, that was an inch x half inch x half inch block.

It's not light though.

Clint Sales sells Merlin's Magic for hobby use.

http://www.clintsales.com/dental.htm

A tutorial sort of thing:

http://www.hirstarts.com/casting/dental.html

thedugan
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Postby thedugan » Mon Oct 27, 2008 5:49 pm

So, how much did you buy (how many pounds)?

Would that be like a pint's worth, a quart's worth, a gallon?

Auto Resin comes in quarts, so I'm trying to get a ballpark idea of whether I ought to use some of my PayPal funds to experiment with this stuff.
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jimbeau
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Postby jimbeau » Mon Oct 27, 2008 8:28 pm

it's a plaster-type powder about $1 per pound all-in all including shipping

for me, I have about 40 pounds left, so I'm going to use it whether it's cost-effective or not.

I'm slightly surprised the mold worked too. But work, it did.

nathan
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Postby nathan » Mon Oct 27, 2008 8:29 pm

It's a totally different material to resin. I'd recommend gettting a smaller amount if you're not familiar with it or know that you want to cast something definitely with plaster/die stone.

I'm heading the opposite direction. I've worked with die stones and dental plasters and am just getting started with resins (started with cheap polyester resin from an autobody supply shop).

The last 50 pound box of die stone I bought was like a foot wide cube. The die stone was bagged inside of that and filled the box up about 90% of the way.

Die stone feeds and feeds into water. You'll be surprised at how much a given volume of water will absorb.

My general thinking is that plaster/die stone is better for some terrain and resin for miniatures. Whether or not I'd go with resin or die stone would be a decision made on a case by case basis depending on the shape of the piece and the nature of the mould.

Also, never dispose of plaster/water solutions down the drain. Always let the plaster set completely and throw it out. Sounds like a no brainer, but it's easy enough to forget and it only takes one time to block a pipe. And even a really thin plaster/water solution will cause a build up over time.

thedugan wrote:I'm not questioning that it worked, just whether or not it's the most cost-effective solution.


My thinking is that for a meteor, the rotating with polyester resin to make a mostly hollow cast might be the way to go. Like the guy did with the rock casting on the taxidermy site.

Die stone is about strength rather than volume, so it takes a surprisingly high weight of dry powder to make a given volume of plaster. So as far as cost effectiveness goes, if you can mix up polyester resin in small quantities and get good results with it, that'll probably be cheaper than die stone. Die stone has the advantage of being all water based with no nasty fumes though. And it's more sandable/workable than polyester resin. Also, less heat is produced, so you can get a longer mould life.
Last edited by nathan on Mon Oct 27, 2008 8:41 pm, edited 2 times in total.

nathan
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Postby nathan » Mon Oct 27, 2008 8:35 pm

jimbeau wrote:I'm slightly surprised the mold worked too. But work, it did.


Did you affix the wooden hexigon to another surface and make a skin that goes wide around it? Or does the mould end right at the hexagon?

Here's an example of what I'm talking about, step 9 and 10:
http://www.myheap.com/book/chapter-07/e ... ple-01.php


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