Budget molding and casting

By neimhaille. 27/05/10, 04:49 am

Hey all. I just posted to my LJ about my mold making and thought I should post it here too ;) While google will cache my lj this is an easy spot for all NZ cosplayers to find info :)

Sculpting materials:
So Static below mentioned using terracota to sculpt with :) I love fine grain clay but haven't been able to get any decent stuff for cheap myself but will be looking into this ;)
Water based clay like this is really good for sculpting. So long as you remember to keep it wet while working. This generally means a damp towel carefully draped over it and a large plastic bag to enclose it. This keeps the moisture even all through and over.
You can also use water to smooth and soften to build up details and to do finishing cleaning. Also of course, water clean up ;)

I use Das plasticine a lot as it is so cheap. I think I have about 5kg of it right now either in untouched packages 9though not for long) or projects scattered about myworkshop (though where my doll head is I have no idea- she was a pretty elf).
This is not the easiest plasticine in the world to work with not compared to the expensive brands. That said there are a few tricks to making it work.
Heat: heat will soften the clay to make it easy to work into big bulky parts. I use a heat gun a fair bit when working on sculpting to soften the surface to allow the next layer to stick better and to help smooth.
I also will use the stove top (with extraction fan on high!!!) to melt my plasticine in a pot. It melts quite quickly being an oil based clay and I then pour it onto sheets of baking paper to store and have a ready supply to thin sheets of it. It's great to be able to cut strips or basic shapes to build up.
I also melt and strain used clay through a double layer of fine netting to clean it for further use. it is the easiest, though can be messy and smelly, way to recycle plasticine that has random bits of plaster or stuff from the workroom.
Cold: In the cold weather we have no I find I am able to carve into the clay for a different kind of sculpting. You can get nice clean straight lines when the clay is hard enough to cut. To do this in summer it might be an idea to make room in the fridge ;)

You can smooth the plasticine with water, acetone or oil. I prefer water- it's the friction between your hands and the clay that smooths it. The water allows you to not stick to the clay when it gets warm from the friction ;) Acetone melts plasticine but not by much and I prefer to leave the acetone for vital cleanups ;)

To clean plasticine from tools and pots etc. Heat the pot/tool and wipe all over with a paper towel, or three. The paper will absorb the melted clay. To remove the residue use lots of dishwashing liquid and hot water. The hot water again melts the plasticine and the soap will bond to the oil particles and carry it away. it's best to remove as much of the clay by scraping itout then wiping out with a paper towel before this process.

Polymer clays can also be used for sculpting and the pros for them include the fact they don't melt if you leave them in the warm (they may cure if you leave them for long enough in a very sunny spot....) and they also come in a variety of hardnesses.
FIMO is rock hard and can be hard to get started (Whitcoulls still sells it- mid priced)
Super Sculpy is really commonly used, a fine slightly powdery grain to it. (Top Mark and a few specialist craft stores stock it- mid priced but you have to buy big blocks of it)
Cernit is the OOK doll makers choice for many years and works to a very soft hand. Best worked on a stand so hand heat doesn't soften it too much. (mid priced, from the Emporiums up here- both Geoff's and maybe others that the different family members own)
Sculpy III- mid priced again and somewhat like Cernit but not so waxy looking with finished. (Spotlight)

To bake them requires heat and it can be very tricky to do so without the clay cracking or burning. You need to be careful when working it to avoid air bubbles as these will expand and cause cracking (just like in ceramics ;) ). Boiling will prevent burning but not cracks for this same reason.

Sculpting tools:
I just recently purchased a set of plastic tools, I think there were 12 pieces and all had double ends. I love them. they were really cheap at $6 for the lot.
I also have a nail kit. The little cleaners you get with them work really well for carving small detail and I use the edge of the nail file to scrape clay back to a flat surface.
I also created a few tools myself. One is a strip of plumbers coil bend into a u shape with a handle for scraping clay. Another is a piece of polymer clay I pressed into concrete and baked. This I used for texture in my Leia costume. And another texture tool I made was from a silicon paint tool that I had ruined (silicon sticks to silicon... oops!) so clipped and cut. It also creates a pebbly texture.

Silicon Molding:
Because I have blabbed all over the place but not actually specified in one easy to find spot. I totally ghetto'd my mold making for my Leia costume ;)

I used silicon caulking. Good old Selley's transparent roof caulking. But how?

This is the super easy and cunning part:

An ice cream container of warm water and any lots of squeezes of dishwashing liquid (I tend to use a little more than strictly necessary but it is better to be safe than sorry). Dip hands in and mix to make very soapy water and get it all over your hands. Back and front, fingernails and all.

Cut off the end of the caulking tube and squirt as much as you need into the container.

Smoosh with your soapy hands until the caulking is no longer tacky.

It winds up squishier then gum but still firm so you can mold any shape and in all directions. I have covered and entire doll's head without the silicon slumping. You need to be careful to avoid air bubbles and apply in a layer no more than 1-1.5cm thick or there is a risk of the silicon not curing. I like to press a really thin layer to get all the fine details and then build up over that.

This stuff is condensation cured meaning it cures in the presence of water. Working the silicon under water means you start the curing process all the way through. The soap just eliminates the tackyiness so you can work with it and wind up with a tack free mold at the end. If you compare the texture from detackified and normal use it is more rigid and slick.

I love this method and it is about 1/3 the cost of two part silicon molding. I wouldn't recommend it for anything other than a mold where you can leave it to cure over night.
Urethane resin will kill this though. I nearly lost my bra and hip molds of my leia costume and would have if I were to continue to use it. But epoxy is fine in it. I have made about five copies of the hip plates after that and the mold is in no worse shape than before. I also have some silicon spray I'm thinking might help recondition some.

I found this method online, not sure where. Most versions of this suggest mixing in acrylic paint or glycerin but it is all still messy and sticky. This is the easiest and cleanest option. Oh yeah but you can use the acrylic paint to colour silicon ;) It works ok. The silicon winds up a little thinner. Cheaper than using a silicon pigment though. And oil paints will colour silicon too. Ditto on making it thinner though.

Oh I also make little keys for a plaster or resin jacket. Which you want in any flexible mold tha thas a jacket!

Because the silicon is condensation cured you may find you can cast things in it that you couldn't in a platsil or other two part.

So no more easy than the proper professional route but another option for those of us on a budget. In fact it may be slightly harder than the pro route ;)

Plaster molding.
The bane of my existence but still a necessary evil.

Mix as per instructions. Nice and easy ;) But it's the application that can be tricky.

If you have a nice flat open back mold (and maybe even the silicon layer above) it is easy to build a wall around the piece (at least 2cm away from the edge to be safe) and pour. And tap to avoid air bubbles. If you pour from a height this also helps to prevent air bubbles.

If you want to cover a large heavy object that you cannot build a wall around and pour over then you will need to get a soft brush and drizzle the plaster over and into all the fine detail.
Then you can soak cotton gauze in the plaster and use that. Just like those crepe bandages but cheaper. I have an old cotton mosquito net that I have been cutting into strips for this ;) You want a very light cotton so the water and plaster will absorb into the weave.

And never ever ever ever ever take the mold off before it is fully cured! It is super fragile until then, even if just "damp".

Next part will be about casting. It requires safety equipment so I want to take time to put it all in order ;)

By Static. 27/05/10, 06:42 am

That silicone molding method looks awesome! If your original sculpt was still squishy, I take it it wouldn't end too well...? Ie, would be squished out of shape by the squishing of the silicone onto it? Does it stick to the original object much?

By **jpwise**. 27/05/10, 06:57 am

Mischa posted a link on twitter to an example on doing it aswell
http://www.conceptart.org/forums/showthread.php?t=180176

Makes for very interesting reading. :)

By neimhaille. 27/05/10, 04:14 pm

Yeah it was that that prompted me to post here in a nice big public setting ;)

The other article talks about another kind of silicon, Selley's does not give of the acetic acid fumes, I've only found one brand that does it locally and it is a silicon glue. I have been meaning to test with it. but at a stupid price per small tube I'm not that keen ;)

I have tried that method, but I personally don't recommend it as it is still so very tacky after. And it has a risk of getting an imbalance of agents and ruining the mold and the sculpt. Partially cured silicon is really mucky and not quite that easy to clean up ;) It clings like a smushy limpet ;) That said it is another option and it may work better for others :) For example I like epoxy resin over urethane though it is messier and takes longer to cure ;)

For squishy sculpts it all depends. I use budget plasticine and it has not been an issue. I'm not quite sure how to describe the texture. It's only slightly gummier than the caulking as it comes out of the tube. You have quite a good working time but you should only use as much as you can work with. If you leave the caulk in the water it will cure faster than in the air, naturally :)
As for sticking, you can work more of less water into the caulk. You can also use the soapiness of your hands to keep some tack to the silicon but not have it stick to you- I tend to only just detackify it and then re-wet my hands to smooth the top layer.

I forgot. I also use a mist of cooking oil (Pam's, I did say budget ;) ) on the sculpt first to help with demolding.

And I have old towels for wiping my hands as terry cloth really helps remove the caulking from hands. I find I tend to get bits of it on my wrists from the sides of the container. paper towels will work too.

By Mischa. 28/05/10, 01:05 pm

this is a newbishy question, but are there alternative to resin?

By Belakor. 31/05/10, 03:28 am

Mischa wrote:: this is a newbishy question, but are there alternative to resin?

Depending on the size and complexity of the piece I have had some success casting with hot glue for smaller, really quick kinds of things that I just need now. Same with Araldite glue (the two pack epoxy) and for smaller stuff, superglue. Not particularly good since it's not what they're designed for but I've had it work... make sure you do superglue in thinner layers though, otherwise you'll end up with a hard shell and a core of glue (ask me how I found that out, Ha!)

Also automotive filler (bog, bondo, whatever) works too, can be a little fragile if it's a thinner piece and it's not much less toxic than some resins but I've got some prop stuff that I've built just from that Smile

The handplates for my Master Chief were cast with filller in a paper/card mould and are still going pretty strong.

Thanks for the tut Michaela! If I can remember this time I'll have to pick some silicone up today and try this out on some new stuff Very Happy

By Static. 31/05/10, 04:07 am

I am so, SO keen to try this out! I'm using terracotta clay (cheaper than plasticine at Goldings, woo!) to do my original sculpt, will have to pick up some silicone and try this out. Can't wait!

By neimhaille. 01/06/10, 02:44 am

@ Mischa: I have some stuff that I think is a kind of "friendly plastic". They are little bottles of plastic pellets I picked up from an emporium years ago to trial. You heat them and they melt and you can push them into a mold. They are really quite sticky when melted.
Not quite as easy as working with resin but ok. And as Belakor says Bondo can work well for some pieces too :)

@Belakor: No worries :) I figure this is good stuff for those who are in a similar position to me with budgets that have priorities such as power and food ;)

@Static: yay :) I have not been able to find cheap water/earth clay myself but I used to loooove working with ceramics :)

OK and having just spent the morning cleaning my pwn plasticine I'll update the first post with cheapo sculpting materials ;)

By Belakor. 01/06/10, 02:54 am

neimhaille wrote:: @ Mischa: I have some stuff that I think is a kind of "friendly plastic". They are little bottles of plastic pellets I picked up from an emporium years ago to trial. You heat them and they melt and you can push them into a mold. They are really quite sticky when melted.
Not quite as easy as working with resin but ok. And as Belakor says Bondo can work well for some pieces too :)

Oh, I totally forgot about that stuff. Probably what that is is CAPA or PCL (Polycaprolactone) plastic, they use it on the RepRap rapid prototypers (kinda like my Makerbot). I haven't used it but it looks like neat stuff... and I totally didn't consider the prop making uses for it sweatdrop

By Static. 01/06/10, 02:58 am

I've found a couple of tutorials for Friendly Plastic - how much did it cost out of interest? Do you remember?

By Belakor. 01/06/10, 03:04 am

@Static I dug up an old post (Link) that has CAPA at "almost $14, for only 100 grams." from Jaycar. That's a couple years old though.

Also found these two links just now:
http://www.zigzag.co.nz/mm5/merchant.mvc?Screen=CTGY&Store_Code=polymer&Category_Code=U
http://www.mindkits.co.nz/_product_47977/100gm_Polymorph_Moldable_Plastic

By neimhaille. 01/06/10, 03:13 am

I got mine for $2/ a small bottle ;) About the side of those bead tubes in haberdashery shops.

@Belakor: great links :) I think there is a thread about the place that might be worth popping that into as well. I know there is a supplies thread somewhere :)

I know people use it in conjunction with Wonderflex to hide the grain, but I haven't tried it myself :)

By neimhaille. 14/09/11, 06:34 am

Just a bumpy update.

Buy the good stuff.

I just bought some cheap silicon to see how it works... yeah no. It looked too matt when it came out, so I figured it was not actually silicon. Not sure what it is, but it looks a bit like acrylic/latex caulk.

The stuff I have been using is Selley's Roofing transluscent. It is a bit pricey just now but is about $15/tube (seems to have gone up by $2 in the last year). Three tubes will make a mold for a helmet (but you will have to make a rigid jacket for it).

So sigh, I can't advice for an even cheaper supply. Though if anyone has found a very cheap brand that works please let us know here ;)

Another bit of advice- use vaseline for a mold release but make sure it is a very thin layer. Otherwise it could wind up worked into the caulk and inhibit the cure or leave a bubble shape in the mold.

I also had some small mold pieces I made two years ago and put a fresh layer of caulk over. It bonded but not as well as when the silicon is still curing (the first week or so) and I think the bonds will fully separate over time and use.

I am now off to make molds with the scrap of sillicon I have left from my last successful foray. Lots of small parts to Shae and I need to make them light up and also make a few multiples. But I need to clean the bad silicon/mystery stuff off first.

By **Rowan**. 14/09/11, 03:20 pm

What do you use/how do you make a rigid jacket?

By Highlander. 27/10/12, 02:33 am

Rowan wrote:: What do you use/how do you make a rigid jacket?

I second this question.

By Mischa. 27/10/12, 07:16 am

Plaster of paris? (at a guess)

By neimhaille. 28/10/12, 03:05 am

Much computer and illness frustration later...

I use fibregass for my jackets :) I recommend glass cloth over matting as it is much easyto work with and less likely to make super messy jackets. Ehem. I may be a tad mucky but matting is not as easy to work with over rounded forms.

Plaster of paris or ultracal are great for latex casting but you do need a pretty thick wall. Too thick really for use as a jacket for silicon. I do have some pieces backed with plaster, but they are flat back molds and the pieces are poured rather than slush cast.

New use for silicon found!

Tamiya acrylic paints mix in very well. Translucent red makes a wonderful meaty red when you mix it through glass silicon. This stuff does stink like vinegar as it is acetic cure, but it does still cure in water.
This is how I made my Regina heart for Auckland Armageddon. I took a small container and squished coloured silicon all over it as per the first part of this thread. Once cured I cut the underbelly and removed the container and then put a thin layer of unoloured silicon over the red. Yay! Gristle!
Small fingertip lights inside made it glow. Sadly by Auckland the lights had died and I only had green and blue left which made for not really great effect ;) The red and white lights were great :)

By Fettman. 28/10/12, 10:47 am

I used fiberglass for the mothermold of my mandalorian helmet too.
Personally I prefer chopped strand mat over cloth, as if you break it up and tease it out a little it tends to shape to rounded shapes and corners far easier than the regular weave of cloth.

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