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Other Stuff => Workbench => Topic started by: Furt on November 07, 2009, 10:37:29 AM
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I am considering venturing into casting with resin, a scary and possibly quite costly area of terrain making.
Can anyone tell me what type of resin is used in a lot of commercially cast terrain pieces, the gray stuff in particular?
Alternatively is there some other product backyard mold makers use?
I am looking to do this as cheaply as possible.
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Don't know how helpful this will be, but here goes.
My local hardware store tends to sell two types of resin. Casting Resin, which I suppose has some advantages when used to cast 'things' and Laminating Resin which isn't as good in casting as CR, but is used to laminate fiberglass on boat hulls, etc.
The downsides of using resin, for me, are;
Resin is thick, so it doesn't flow into especially thin parts of your mould, and bubbles tend to stay inside and not float to the surface. Perhaps you might try non-expanding urethane (sometimes spelled eurythane). It's reasonably priced, compared to the cost of the silicone moulding compound it's frequently used with. Try looking up a company named Silpak. They're here in the US, but might ship overseas, or even have a local distributer. I'll use resin for stuff like boulders, but not to cast up sombreros, kepis, etc.
Resin is not so great to sand. Our local group has sollved that problem by using something we've named Hooverite. (Because the chap who invented the technique had the last name of Hoover.) Track down some ceramic automobile body repair putty. In the US it's usually refered to as BONDO, but that's a specific product name. Bondo is ground up ceramic suspended in resin. If you haven't used it, it's around the consistency of butter, you mix in a catalyst, and it sets up pretty fast. But you couldn't cast with it. To make Hooverite you buy a can of Bondo, buy some resin, pour the resin into the Bondo, and stir it up to make 'Thinner Bondo.' You can use the same catalyst that comes with the resin to harden the Hooverite. I sometimes mix in the Bondo catalyst as well, not becuase it makes it set up any faster, but because the color of this catalyst helps indicate when I have the Hooverite fully mixed.
How do you intend to make your moulds? If you're just thinking about rocks, etc. you could use 'Press Moulds' created by pushing a master into sulfer free modeling clay.
Hope that this helped.
Regards,
Maj. Weenie
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Resin for terrain pieces can be quite expensive, since you're putting in a lot of resin into a typical terrain piece.
I would recommend looking at products from "Smooth-On", which features resins that can flow like water into molds, as well as many other viscosities. If you want to start experimenting with resin, you can always try Alumilite, which sells resin casting kits in many hobby shops in North America (not sure about elsewhere). Alumilite is a thicker resin that flows like honey.
If you plan on working with resins, make sure you take appropriate precautions. Some resins can give off toxic fumes as they set up, so working outdoors or in a well-ventilated area is crucial--and good practice in any circumstance where you work with chemicals. I'd also suggest using a vibrating table to help loosen up air bubbles that may work their way into the mold as you pour the resin--it's not as effective as (nor as expensive as) a vacuum chamber, but it can help.
Molding compound can be acquired from Dow Corning, Smooth-on, or Alumilite.
I've played around with Alumilite, creating masters from Super Sculpey and molds using alumilite molding compounds, and had fairly good success with it--even with fairly complex 3-part molds.
To get the best value, you're going to have to buy resin and molding compounds in bulk. Even so, it can still get pricey.
One other option you may want to look at if you are casting terrain pieces, is to use Plaster. Check out Hirst Arts for tutorials on plaster casting. Plaster of Paris is dirt cheap, especially compared to resin, and works great for thicker castings. Or you can try harder plasters like Dental Plaster.
Have fun!
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I'll second the recommendation for Smooth On resins. The quality and consistency are well worth the little extra you will pay.
Here is the web site for their Australian distributor. I use the Smoothcast 300.
http://www.rowetrading.com.au/ (http://www.rowetrading.com.au/)
You can lighten your pieces reduce the amount of resin in a casting by using an extender make out of micro bubbles. The Smooth cast 300 costs about $85.00 for a two gallon kit. (1 to 1 mix ratio) from my distributor in the states. A gallon of two part mold rubber runs about $120. To give you an idea of resin yeild, I can get about 14 buildings like this out of a two gallon resin kit.
(http://www.rotanddrivel.com/2smallwindowends.jpg)
The building measures about 3.5x8x7 inches.
Hope that helps.
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I use polyester resin, the same as for fiberglass stuff. Its cheaper. Also I use grey pigment as it helps to see detail.
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you may need a Polyurethane Fast Casting Resin with Polyurethane black pigment....
not done any commercial resin casting yet...but the best stuff we've used is the G6 urethane Biresin from Tiranti, a 2 part resin which is Very fluid, with an easy mixing ratio (1 : 1) and very quick setting, it has a 5 minute pot life and a 30 minute cure. It's a cream colour...to make it grey we just add a small amount of the black pigment.
a couple of commercial wargames resin casters in the uk get their stuff from Mouldlife (http://www.mouldlife.co.uk/) but they don't deal with individuals at present..
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I've always heard that for a quality job you need a vacuum chamber to get the air out of the resin. Is this true+ And here could I get an affordable vacuum pump for hobby use? (No smutty replies please...)
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I've always heard that for a quality job you need a vacuum chamber to get the air out of the resin. Is this true+ And here could I get an affordable vacuum pump for hobby use? (No smutty replies please...)
yes..vacuum moulding/casting does give better results.....although it's also depends on the resin used, mould quality, size of casting etc.....i've never used a chamer and so far had good results with the biresin, although most things we've cast are small and chunky so they tend to cast quite easy and bubble free.
if you can afford a chamber, have the room for one and are thinking about commercial casting...i'd say get one......trouble is they tend to be quite expensive
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If you're doing anything complicated or with lots of detail then really you need a vacuum chamber. Also if you're casting commercially and getting saleable casts every time matters then you also need a vacuum chamber.
Cheapest one I've seen recently was £400 for chamber and pump, but that was second hand on ebay.
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When I cast resin into my mold the first cast shows where the bubbles are most likly to form, so I use a 6inch long copper wire, very heavy guage, with the tip filed smooth to run around in the mold to chase the air bubbles out. Just an idea of how I do some of my casting, especialy for figures.
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One company that I haven't seen mentioned is Micro-Mark -
http://www.micromark.com
they have mold making silicone as well as casting resins. While I have never used their casting resins I have used their 10:1 mold rubber and it works just as well as the Smooth-On product although it is a bit more expensive - it seems to me to be basically the same product. I would stay away from their 1:1 silicone as it tends to be too brittle. And they ship world-wide! I have talked to others who have used their casting resins and have been told that they work well even without a vacuum chamber. You just have to be careful which resin you use - longer pot life = fewer air bubbles - generally speaking.
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I'm from Italy, (the really other side of the world, for you), but I'm pretty happy using PROCHIMA SYNTAFOAM 1.1
it is more fluid than honey (like olive oil) and I hardly find bubbles in my products. It is pretty expensive (around 100 - 110 US$ for two gallons), and I'm looking for a cheaper one for cheaper casts and less detailed parts...
I'll follow this topic, if someone has also suggestion for me, I'm also into this stuff since a short time! :)
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I actually posted this image earlier when someone was asking about 'Bell Tents.' Here it is again, with a pair of Wagames Foundry figures in frame to give scale.
It's cast out of 'Hooverite' the mixture of Bondo and casting resin that I mentioned in a previous post. It's a simple 1-piece 'Drop Mould' without any bottom.
When I read the first post I thought you were considering methods to cast up hills, rocks, etc. But it seems that you might actually be interested in buildings. If so, my recomendation would be to construct/sculpt the front wall of the building lying flat on its back. It wouldn't be very thick, and you could them make a drop mould of that. Then cast it up, pop it out of the mould, and tilt it up to vertical for the front of your building. If you were making row houses then you'd only need to make moulds for the house fronts. If you were really energetic you could make multiple moulds for several fronts, backs & sides. Then mix and match them.
Helpful-Maybe,
MW
PS - I still haven't looked up the web site for Silpak, which is the two part casting urethane that I like best.
(http://thebengalclubla.com/images/belltent.jpg)
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I'm sorry to raise a dead thread, but I though it's better bump it to avoid redundant threads.
I'm thinking also to get into resin cast, I have read is better to use acrylic resins than polyester resins, they don't release toxic vapours, they are less aggressive with the silicon mould, and because they are water based it's easier to clean the tools.
Seems acrylic resins are all advantages, but as far as i see everybody is using other kind of resins.
Anyone has experience on acrylic resins? is any difference on detail level and viscosity between each type of resin?
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I haven't done anything with casting since plaster skulls in university, but I do remember a very nice article on the subject of eliminating air-bubbles and the like.
Rather than using an expensive vacuum pump, you can build a rotocaster. It's not as good as a vacuum pump, but can be built quite cheaply and still gives you a lot more options and better mould penetration that you can get with plain regular sit-n'-pour.
It was an old ShiftingLands article and can be found here (http://www.shiftinglands.com/tips&tricksrotocast.htm)
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I'm thinking also to get into resin cast, I have read is better to use acrylic resins than polyester resins, they don't release toxic vapours, they are less aggressive with the silicon mould, and because they are water based it's easier to clean the tools.
Seems acrylic resins are all advantages, but as far as i see everybody is using other kind of resins.
Anyone has experience on acrylic resins?
(raises hand) I've used acrylic resin. There's two basic kinds of acrylic resin: emulsion, and thermosetting. What you're describing is the former, but the latter is what's actually used for casting.
Acrylic emulsion is what's used as a media in acrylic paints, and is not at all suited to casting. It cures by having its carrier solvent evaporate out, and usually shrinks a lot (for a casting media) in the process. It also tends to be a bit weak and flexible (again, as a casting media) when cured. Imagine trying to cast an object out of solid PVA glue and you'll have an approximate image of why acrylic emulsion isn't used for casing.
For casting you'd want a thermoset acrylic resin. Unlike most two part resins, the A and B components come as a liquid (very low viscosity, like water or alcohol), and a powder respectively. The stuff makes wonderful finished pieces, and is very easy to use and forgiving to work with, but it's also insanely expensive, produces nasty fumes, and is actually much harsher on molds than urethane or polyester resins. It's fantastic stuff, but its downsides make it kind of a special purpose material from both a personal hobby and kit production standpoint.
is any difference on detail level and viscosity between each type of resin?
Not categorically. Mostly for casting you'll be dealing with one of three types or resin: polyurethane, polyester, or epoxy. The rest is mostly down to the specific manufacturers formulas and product lines. When people recommend different resins, you should take that as recommending a particular brand and/or formula, not as a blanket statement about that type of resin in general.
There are some generalizations that can be made:
Polyester resin is what fiberglassing resins and body fillers (like Bondo) are made from. These are the cheapest and easiest to get, and are fairly easy to use. These are popular among garage level gaming terrain & vehicle producers for this reason. Polyester resins shrink more and take detail less precisely though, so they're best used for things where exact shapes are somewhat negotiable, and are not suitable for figures or anything that requires higher detail fidelity or precise part fit. The resin by itself tends to be brittle, and needs fillers to strengthen it. Their relatively low precision means you rarely see them used much outside of the gamer-targeted market.
Polyurethane is the most common casting resin type. There are many brands and formulas with many different working and finished characteristics, so these are the most versatile. Generally they are stronger than polyester, and take detail better than either polyester or epoxy. They are also more expensive than polyester, and require more careful attention during mixing and casting. Clear polyurethanes in particular are notorious for requiring very specific procedures and conditions in order to turn out properly. These are what you want to use if you're making figures, or vehicles/structures with higher and more precise levels of detail. Do your research: look at the companies' websites, and read over the material specs for the different product/formula lines before buying, as these do vary a lot. Some will be brittle as sugar, and others tough as iron, some will be thick as honey, and others will pour like water, and everything in between. Polyurethanes can make for more detailed and more durable models than most any other material, but you have to use the right one for the right job: most of the rep resin has for being less durable than metal and suchlike is down to manufacturers who weren't being choosy enough with their materials.
Epoxies are mostly used for protective clearcoats ("finishing epoxies"), higher performance fiberglassing, and of course glues and putties. There's more variety to them than polyesters, but lass than urethanes, and they tend to be more expensive than either. Aside from fiberglassing or production-level vacuuform molds, you don't see them used as casting resins very much. You can use then as such though. They tend to be rather on the viscous side, but that can be improved a lot by cutting them a bit with alcohol during mixing, and they can even be tinted using ordinary paints. These will be the least damaging to molds, and most of the consumer level ones will be less toxic than the others (though they are a sensitizer material, meaning over exposure can cause you to become allergic to them). Epoxies also make for very durable castings, though if you pick right, that's easy to match with urethane. They can take detail better than polyester, but not as good as a higher performance urethane.
Acrylic casting resins are the most expensive by a wide margin. They take detail as well as mid range urethanes, but they shrink a bit more and are much harsher chemically. They are impressively durable, but are also very easy to sand and scribe, and are the easiest and most forgiving of the lot to mix & cast.
Again, though, these are very much generalizations. Individual brands and formulas will vary a lot, and so will the needs of different molds/castings, so your need to take any recommendation for or against a particular resin as pertaining to that specific brand and/or formula, for that specific use.
Also your choice of mold rubber has to be matched to your choice of resin. There are many different brands of mold rubbers too, and they will give better or worse results for different resins and different shapes. Some types or rubber won't play well with some types of resin chemically, causing the resin to set up gooey. The best thing is to buy your rubber and resin from the same manufacturer, and read the documentation beforehand to make sure they're compatible, and that the rubber is the right hardness and flexibility for the size & shape of the object you're casting.
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Good things come to those who wait!
A very thorough and detailed reply - albeit a little late. :-[
I have since used the two-part liquid resin to great success and have also experimented with dental plaster, which is OK for simple "blocky" casts.
Regardless I'm sure others will find the reply very useful.
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In regards to vacuum/pressure casting, the setup cost is kind of high. Sourcing and buy the components separately is cheaper than buying a packaged setup kit, but it does involve more time and labor though, so whether it's cheaper on the whole depends on whether you're factoring that into the cost. Expect to spend a minimum of $300 US to get started in pressure casting, and that's if you already have an air compressor.
You need the compressor, a vacuum pump, a pressure chamber, a clear alternate lid for the chamber, plus gauges, hoses and fittings. A small (two gallon) chamber and suitable vacuum pump will run you roughly $100 each. Fittings are cheap individually, but they add up fast, so expect to spend around $20-30 there. You'll need a piece of clear acrylic sheet for the vac lid, which will cost you anywhere from $15 to $40, depending on specs and thickness (I used a 1x12x12" piece of cell cast acrylic for mine, which was about $30 plus shipping. It probably didn't need to be that heavy duty, but I wanted a wide safety margin), plus another $15 or so for a drill bit and tap for the hose & valve fitting. I cut my lid gasket from a foam counter top traction mat, so that only cost me $4. I already had a compressor, but if you don't, then tack on another $100 for that.
If you're just casting parts for personal use, the best thing IMO is to just get a resin that sets up very slowly. That way you can spend time on each pour making sure that everything gets distributed throughout the mold properly, fish/knock out bubbles, etc. You can get very good castings that way alone, if you're resin allows you the time. IMO you only need a vacuum/pressure setup if your molds have really fussy details, or if you're casting in volumes large enough to make quicker setting resins necessary.
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Good things come to those who wait!
A very thorough and detailed reply - albeit a little late. :-[
I have since used the two-part liquid resin to great success and have also experimented with dental plaster, which is OK for simple "blocky" casts.
Regardless I'm sure others will find the reply very useful.
I've been a member here for less than a year. The original thread was before my time.
A sticky on casting would be a good idea IMO. It's something that's bound to come up repeatedly, and I know there's people around here who are much more experienced than I am who might contribute.
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I've been a member here for less than a year. The original thread was before my time.
No offense meant Connectabob, I'm merely a bit envious your obvious knowledge of the subject was not available to me earlier. :)
As stated a sticky on casting would be very useful.
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wow! thanks a lot Connectamabob! thats a clear an enlightening reply.
I found a seller not too far from my town with a nice assortement of resins and silicons
http://tienda.resineco.com
they have acrylic and polyester resin but no trace of uretane ones, and something called jesmonite, they describe it as a kind of acrylic resin compound for mould casting, but looking at the manufacturer website it only display resin's architetural applications
http://www.stevensons-of-norwich.co.uk/service/jesmonite/
any feedback about the jesmonite?
these guys (resineco) also have a blog (only spanish version available, sorry!) with step by step tutorials of simple mould casting, using their products of course, but still interesting as a begginer guide IMO
how to make a silicon mould
http://resineco.blogspot.com/2010/04/como-hacer-un-molde-con-silicona-para.html
how to cast resin copies (using this Jesmonyte stuff)
http://resineco.blogspot.com/2010/04/copias-con-molde-de-silicona-y-resina.html
the vacuum chamber is completely out of my plans (and my budged) I was considering the fishing bubble option, or event to build some kind of vibrating surface (if that would help float the bubbles)
i agree some kind of sticky about resin casting will be really helpful
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The Jesmonite stuff is new to me. Looks interesting though. I dug about a bit online, and found that it's an acrylic/gypsum hybrid material. From what I gather, it's like a kind of plaster that uses an aqueous acrylic in place of water. Interesting concept, and I'd love to see more details on how stuff made from it turns out.
some more info:
http://www.abic.se/pdf/Jesmonite%20AC100%20User%20manual.pdf
http://www.artrocker.com/rrpedia/Jesmonite
http://www.youtube.com/watch?v=GRZQ7URVGKM
http://www.youtube.com/watch?v=OvUgH0SumaI&feature=related
The blog links are interesting. Good instructions, though there are a couple of things I'd have done differently. Single-part open faced molds are popular, but few garage manufacturers do it right IMO. You want the mold face to be nice and flat so that you can use a backing during casting.
In the case of the blog demo, I'd take a sheet of MDF or melamine board and drill holes for the magnets so the turtle sits flush, chop the lip of the plastic container down to the intended depth of the mold and drill two large holes in the bottom, then place the modified plastic container upside down over the turtle, and pour the rubber through one of the holes in the container bottom 'till it's full. After demolding, trim another couple mm of the lip of the plastic container (to account for slight shrinking of the rubber), and you've got a finished mold with a nice flat face, with the modded container serving as a mother mold.
Once that's done, trace the "footprint" of the original pattern (the turtle) onto a cheap polyethylene cutting board, and drill a hole in the middle of the tracing (the size of the hole depends on the size of the pattern/casting, for this I'd say maybe 1cm). This is the mold backing. It ensures an even, flat back on the finished casting, and the hole acts as a vent and reservoir to allow the resin to shrink as it cures (all resins shrink, some just shrink more or less than others) without distorting the flat back of the part.
For casting, set the mold in its dish cavity side up, pour in the resin 'till the resin surface bubbles above the mold surface, then press the backing down on top. Alternatively you can start with the backing on, and pour the resin through the vent hole.
Many garage manufacturers who use open faced molds don't use backings, so you get all kinds of over and under filled edges that need to be sanded or filled or otherwise repaired before they can be assembled. The only good excuse for this IMO is being a newbie.
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the vacuum chamber is completely out of my plans (and my budged) I was considering the fishing bubble option, or event to build some kind of vibrating surface (if that would help float the bubbles)
For vibration you can just leave the mold on top of a running clothes washer or drier. If the parts you're casting are really simple and your resin really fluid, you can even just knock it a couple times on the bench top.
Before you pour the resin, dust the inside of the mold thoroughly with talc. The same properties that enable silicone molds to be used without a mold release also make it very surface tension friendly, and that's one of the reasons bubbles can get trapped in details so easily. The talc will break the surface tension of the resin so it flows into the wee nooks and crannies of the mold easier.
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No offense meant Connectabob, I'm merely a bit envious your obvious knowledge of the subject was not available to me earlier. :)
As stated a sticky on casting would be very useful.
I may tidy this up and put it in How to
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Good move that man :)
cheers
James
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I have a vacuum pump that is in parts in a box. Its not running at optimal performance, I thrashed it somewhat. I works, but doesnt ever get to a really low pressure. It gets to the point where it sucks the bubbles out, but its inconsistent and annoying.
However, it would be a great pump to start up with, and Im happy to send it out for nothing, just the postage costs. Im in the UK.
It needs to be reassembled, and I dont have the instructions!
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I have a vacuum pump that is in parts in a box. Its not running at optimal performance, I thrashed it somewhat. I works, but doesnt ever get to a really low pressure. It gets to the point where it sucks the bubbles out, but its inconsistent and annoying.
However, it would be a great pump to start up with, and Im happy to send it out for nothing, just the postage costs. Im in the UK.
It needs to be reassembled, and I dont have the instructions!
I shall be interested. how much should the shipping cost be?
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Many garage manufacturers who use open faced molds don't use backings, so you get all kinds of over and under filled edges that need to be sanded or filled or otherwise repaired before they can be assembled. The only good excuse for this IMO is being a newbie.
I have a newbie doubt, the use of backings sounds really cool idea. I suppose, while casting, you put the back after some bubble fishing, but even with the vent hole on the back this would make the expel of bubbles more difficult, is'n it?
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Now with a nice air compressor in my possession (capable of holding at least 8psi) I have been toying with the idea of acquiring a pressure chamber with an removable lid for plaster and resin casting. It seems like the easier alternative to remove bubbles. I saw a web page with a fellow building his own not to long ago. Can't remember where, forget my own head next.
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I'm going to making my own vac chamber soon as we now have a moveable compresser at work :)
cheers
James