Monday, September 24, 2012

Blurp, Blorp, Smoosh

Last week I took a class. An awesome class.  A class that makes you glad you're an adult who has finished regular school so you can spend a whole week doing this sort of class.

A class, in short, in mould-making and casting, skills which are very useful to my Props students and which I, until quite recently, had absolutely no hand in. But no more!

Yes, I, your humble narrator, am now absolutely teh awesomzors at pouring silicone on knick-knacks.

I've uploaded photos in chronological order, starting with Tuesday, as I forgot my camera Monday. I had a classmate and a teacher, but in the interest of courtesy I have excluded photos of them and their work as I don't really know them. But their work was quite good--in several instances, better than mine. Anyway.  The shot at the top is at home this past Saturday at dinner. You'll see. Pictures!

This is my 3D mould of a candlestick the morning of day 2. The original candlestick is encased inside. By this point I had poured and smeared silicone all over one side, and had let it harden overnight. I then made a trough around it and filled that with plaster, which sets up quite quickly (less than half an hour). The little dots help everything line up when you're reassembling it. The plaster jacket poured around it holds the silicone mould in the right configuration while the casting medium sets. Everyone catch that?

Your humble narrator MISSING A HAND OMG WTF AAAAA  graciously volunteered to demonstrate how Alginate works, an algae-based form-taking compound that typically works exactly once, but very quickly. Only used for safely taking moulds of people's parts, you slorp it on fast (and cold!) and let it set (in about three minutes). Then gently remove (in my case, I wiggled my fingers and it came off) and fill with plaster within an hour to get an amazing copy.

My hand, supported in rice, waiting to be filled with plaster.

Not bad, eh? Embiggen for detail. The alginate mould was, unfortunately, destroyed in the process of removing the plaster cast, but that's normal. Now I could mould the hand in silicone, which takes at least 8 hours to set up, without my fingers cramping up for 8 hours. 

My original candlestick, with its freshly-cured and freed plaster shell, waiting for its second silicone layer.  Neat thing: with enough petroleum jelly, the silicone and plaster you see here will not stick to the silicone and plaster you pour to make the other side, so the dots just form themselves! Poured second silicone layer and put aside.

Cookin' up some vinyl. Yum. It smells like custard-scented plastic, particularly so when you  melt it.  It gave me a headache.

My classmate pouring vinyl over an ashtray she would like to use as a lamp base. The vinyl takes a couple of hours to cure, so we left these overnight.

Wednesday morning. The brass-coloured coin on the right is the original, found in a pencil-box in my house.  I think it belongs to my landlady, though what its significance is (if any) I couldn't begin to guess. The yellow form above it is, you guessed it, the vinyl mould. The terracotta-coloured mould and block above are modelling wax (very very soft, smearable, smells like crayons) and the off-white set are Sculpey.

Wahoo! After a quick plaster-pour and set in the morning, the candlestick decanted beautifully. Silicone is amazing--it even copies the sheen of the original. The belly of the knick-knack is ever so slightly satin-textured, and that will reproduce accurately no matter how many times you use it (which could be an indefinite number with reasonable care). My classmate's prototype was glossy ceramic, and it transferred the gloss perfectly.

Cutting air-vents into some fiddly bits to prevent bubbles getting trapped. The vent must carry straight through into the rest of the piece.

GIANT CHRYSALIS. Or mould wrapped in cling-film ready to have plaster poured in it and shaken vigorously. 
Plaster poured, time waited, cracked open, success! Well, not really success--I mixed the plaster too thick and it set up a bit too fast, so there's more bubbles than I would have liked, particularly near the bottom (the last part I poured, by which point the plaster was already setting up.) Whoops.

But hey, my air bubble vents worked! Everything seeped out nicely.

Cleaned up and tidied. Did you know you can cut freshly-cast plaster with a scalpel? I do now. I finished up the bottom later.

As a curiosity, my teacher coated the handle in a thick paste-like silicone and let it harden over night, just in case. It came in handy. We also poured 2D moulds in silicone and left them overnight to cure.

Original at the bottom, while the top two are a study: both copies are made with a plaster compound mixed with iron for strength (and to give it a nice terracotta appearance) but they are resting on their moulds--vinyl to the left and silicone to the right. Embiggen for detail--you'll see that the vinyl one looks nicer, nice and smooth, but the silicone one, while rough and kinda crappy-looking, is actually a perfect copy of the original. Vinyl doesn't take absolutely the best copies of things, but it has three very distinct advantages over silicone--it is slightly cheaper, it sets up faster, and it can be melted down and re-used over and over. But silicone does the job far better.

Thursday morning. A shell being copied in polyurethane resin, padded out with Fillite, a lightweight industrial ash that is used to stretch polyurethane (as a cost and weight-saving measure). This process involved swirling the plastic resin carefully around the mould until it hardened (well, until it stopped moving).  It sets up in about twenty minutes. 

The shell to the left is pure polyurethane, no filler. The shell to the right is With some barnacles. But they're long dead. My landlady had about eight of these.

Check those deets! Polyurethane's potential for producing accurate replicas is OFF THA CHAIN. 

My teacher's genius idea for adding increments to disposable cups. Only works if you regularly use the same cups, of course, but this style is pretty easy to find, and dirt cheap. Great for polyurethane and polyester mixing. 

Oh dear, this is getting a bit silly. Original at the bottom, then a polyurethane copy with faux gold leaf powder added to Part A. It was lightweight and shiny but the gold comes off if you rub it. Then a polyester copy, filled with actual bronze and copper powders. Quite heavy, and polish-able to an antique-like glow. Then the two terracotta plasters, then wax, then a cruddy polyester one from the vinyl mould (made with leftovers, hence it is not full), then sculpey, then polyurethane/gold leaf in vinyl (again, leftovers). It gets worse.

Now it's your turn!

A polyester/metal powders apple, using a mould that was laying around. I've polished it a bit with steel wool to bring out some highlights. It is very cute. This was Friday morning.

A polyurethane copy of my candlestick's handle, with green pigment and faux steel powders mixed in. The steel just darkened it, really, which I think gave it a slightly antique-y feel. It was an experiment. As you would have noted earlier, polyurethane cures opaque, so suspensions in it don't show up very well.

Set handle copy in the mould for hollow cast attempt. The hollow-mould technique probably would not have gotten enough PU into the handle space for it to work otherwise.

Photo down the bottom of the mould to check how it was all curing in there.  Looks good!  Hollow PU casting involves rolling it around and around and around and around until it stops moving. Takes a while but it saves money on resin, which isn't cheap. Pretty much nothing involved in the mould-making and casting process is cheap.  The copy came out really well but I forgot to take pictures of it and my camera battery is dead. Maybe I'll update this after I take a picture. 

So yes, I learned something. A thing or two. I learned a lot of other things that aren't detailed here but these were some of the cool things. I also really enjoyed it. I screwed up a few times but was able to figure out what I'd done wrong (mostly speed and thickness-related issues that get better with practice).  The things I brought home look nice, and I'm proud of them, though what on earth I'm going to do with them now I have no idea. I'm back at work this week, ho-hum. Maybe next summer I'll take a class in ceramics. Or sculpture.  Or blacksmithing. Or silver-smithing. Or painting nudes. Or painting naked people.

MOAR! Just two--the middle ones are Jesmonite, a type of plaster that is mixed with a plastic polymer for added strength. The yellow one is Jesmonite with chrome yellow pigment powder, left over from my classmate's hollow cast. By the time I'd made my 10th copy I was giggling like a moron. I'm rich! I'm rich! I'm awaiting the arrival of my clear cast polyester copy, in a translucent blue with glitter. (classmate's idea). It wasn't set up by the end of class Friday so the teacher said he'd put it in the post, along with my vinyl mould and a few other things we poured.

1 comment:

Kim said...

How cool! So much fun to take classes and learn new shit, no?