Thursday, July 31, 2008

Molds, Molds, Molds...

And here begins the plaster mother mold section of the moldmaking process...

First you need:

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Lots of burlap cut into squares. Check.

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Lots of vaseline. Check.

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And lots and lots and lots and lots of plaster. Check...oh wait no we ran out and had to order more midway through...but we got it so Check!

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After applying a thin coat of vaseline to the rubber, metal and the base, we mix up a bucket of plaster. We've been doing 16lb mixes at a time, as its seemed to be enough for both of us to use and not run out of too fast yet it doesn't set up before we're done.

A little about the plaster, we're using a mix of FGR and pottery plaster (Usually we use molding plaster instead of pottery plaster but they seem to work the same). We dry mix it first and then use a 1:3 ratio for water to plaster (4lbs water:12lbs plaster). We add the plaster to the water, let it soak in for a little while and then mix it using a mixer on a drill. (Using the mixer gives you a nice consistency.)

We then use brushes to paint up the first coat of plaster (as seen above), staying within the shim of section we're working on. At first the vaseline resists the plaster a bit which is always a pain, but as it thickens it stays up.

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Closeup of splash coat being applied.

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Then we go in for a second coat, where we coat pieces of burlap with plaster and over lap them across the whole ends up looking like a terribly uncomfortable patchwork quilt or something like it...

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In this photo you can see a bit of texture difference between the area with burlap (the bottom half) and the area with just a splash coat (the top half).

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We then go in with another coat of burlap over the whole thing. After that, we further build up the edges of the section of the mold using more burlap and thickened plaster.

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After starting the 2nd side of the mold.

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2nd side with splash coat.

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Here you can see how we end the plaster at the clay wall. Before working on the piece to the right, we'll remove the clay wall and vaseline the plaster edge of the first piece so the two pieces don't stick to each other.

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Working hard...


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If there's one part about mold making that I hate more than anything, it's having to attach clay shims to rubber and having them fall off in the middle of making the plaster mother mold. Enter husband, Justin aka problem solver extroidinaire...We don't usually use metal shims with rubber molds but he thought it would be a nice way to cut back on the amount of clay shims we needed to use. (FYI- A shim is used to divide the mold into sections that will end up being pieces of the plaster mother mold.) To get them to stay he cut a slit in the rubber T and inserted the sheet metal in about a quarter inch. He then used packing tape to attach the pieces, in order to make sure plaster doesn't get in between the pieces of metal.

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Justin demonstrating how fancy he is.

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All metal shims in onto the clay shims...

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Intern Nora making clay shims.

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Clay shims!

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Clay shims added to the rubber. This divides the mold into 7 pieces--3 on each side and 1 on top.

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You can see that we back the clay shims (aka clay wall) with smaller pieces of clay. They act kind of like buttresses and hold up the wall while we're working on the other side of it.

Next up plaster mother mold...!

Finished Rubber Mold

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This is the finished rubber mold. It's about 5 coats of rubber and the whole thing probably weighs about 120lbs...!

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The large strips along the center line of the piece are called "T's". These help the rubber key into the plaster mother mold that we'll be making next.

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This is what a "T" looks like in cross section (Upside down but you get where the whole "T" thing comes from, no?). Each T is solid rubber with no thickener added. Usually the T's we use are smaller but Justin made a special larger T mold for this project. (I forgot to take a photo of it...)

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This is a strip mold used to create rubber strips that are about 2.5 feet long by a half inch wide by a quarter inch high. These are placed on the large surfaces of the mold to also help it key into the plaster mother mold.

Up next: Shimming the rubber mold!

Monday, July 14, 2008

Rubber, rubber everywhere...

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Justin built these bucket dumpers to make for easier pouring, which is nice. We're using Polytek 74-29 rubber, which is a 2 part mix (by weight or volume). Each bucket weighs 40lbs when you start so it's nice not to have to hold and pour them.

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We used these buckets and 2" chip brushes for the rubber. This size bucket is nice because its easy to handle while trying to paint rubber at the same time. This size brush was perfect for this piece.

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We started out using 3lbs of rubber and quickly saw it wasn't enough and ended up mixing another 8lbs. That did the trick quite nicely. We painted an even layer over the whole thing, touching up spots that looked thin as we went.

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The bucket dumpers after breaking them in.

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Me painting up rubber.

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1st coat of rubber finished! We'll let this set up and then move on to the 2nd coat.

Sealing and Prepping

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Me and the finished boot.

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Time to coat the boot with spray shellac. This will seal the clay a bit and help keep it from cracking while we get ready for the mold.

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Always wear your respirator!

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Justin spraying on the shellac.

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Next we put the clay walls around areas the rubber will run down into.

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Now it's time to put vaseline on the base. This makes sure the rubber won't stick to it.

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Justin applying the vaseline.

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Next we sparyed on 2 coats of Pol-ease to release the boot. This makes for easier removal of the mold when its finished. (Wear your respirator! This stuff is terrible to breathe in!)

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The boot, sealed, prepped and ready for rubber!

Next up, rubber!

It begins...

The mold of the giant boot is started. I'm 1 coat of rubber in and here's a little step by step visual of whats going on:

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Justin building bucket dumpers.

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Assistant Aubrie making clay walls.

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Some finished clay walls (We actually ended up cutting these in half for a shorter wall...)

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The plastic room Justin and I build. Keeps airconditioning in and toxic checmical smell out of the studio. (yes we have an exhaust fan in there so we're not killing ourselves with fumes...)

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The wrapped boot rolled into the plastic room. (Does anyone watch Dexter? This very much reminded me of that show...without all the blood I guess.)

Next up...Sealing and Prepping!

Thursday, July 10, 2008

Mail Order Moldmaking...

One thing that anyone who I'm close to knows is that I LOVE getting mail, of any kind...letters, packages, emails, text messages, notes in my lunch box, etc...
And one thing that I love about getting ready to make molds is that I get LOTS of stuff in the mail...


400 nitrile gloves (latex allergies be damned!)
96 2" Chip brushes (!)
160 lbs of rubber (!!)
4 lbs of plastic (for testing casting methods)
2 cans spray release
1 gallon of expensive mold coating...(let's hope it works REALLY well...)
10 lbs of Polyfiber
4 lbs of pourable expanding foam... (for testing)
362 T-pins
And lots more to come...

Be on the lookout for a step by step photo guide on how to make a rubber mold on a giant boot...(You know, just in case you ever find yourself in that situation. ;)

Wednesday, July 2, 2008

My what big sculptures you have...


Don't mind the funny picture of me...Just wanted to prove that yes, I am REALLY sculpting a giant boot. And yes, it's REALLY almost done. Just put out the call for some interns to help with the moldmaking/ casting and heard back from 3 people which was awesome. This is exactly the kind of crazy thing I would've wanted to work on either while still in school or just out of school.
One of the first big jobs I ever had right out of college was to sculpt farm animals for a children's exhibit in the State Museum of Harrisburg. I was working for Kitchen Sink Fabrications and we had to make a life size sheep, 2 lambs, a big pig, a little pig, an over life size rabbit, an over life size snail, an over life size bee, about a million carrots and cabbages (for the kids to "pick"), AND A GIANT CHICK!!!
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I worked on this pig was so weird looking with the realistic glass eyes!

Me, Doug and Justin pouring the silicone rubber that the pigs were cast in. (This took forever!)

Finished pig!

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And I got to sculpt the maquette for the giant chick. It was scanned into CAD using a 3D scanner and a steel frame was build for it. It was then covered in fiberglass and spray foam, and THEN covered in sheep's wool (weird right? It really worked though...soft and know, like a baby chick!)

I told you it was big...
The Sheep family and baby pig.
Giant snail! (Made of silicone rubber and fiberglass.)

Stages of a bees life. (This one creeped me out...I wasn't a big fan of the bee larva)

Carrots and Cabbages for picking. (Not eating...they were made out of rubber and foam!)


And me with the giant chick. Funny, no?