Monday, July 18, 2011

Hirst Arts Elements: Casting Time Of Zero

One of the questions posed to me the other day, about casting Hirst Arts molds, relates to the required time for casting the plaster elements. Sadly, the casting time for Hirst Arts is NOT zero.

However, with a little planning, you can complete one mold every six minutes.
Here's a series of photos showing the Hirst Arts casting process. In addition to the Hirst Arts molds (in green, plus one of my own molds in pink) you will need some plastic cups, water for mixing with the plaster (in the Indiana Jones popcorn bucket) and a soaking tub for your molds, complete with jet dry mixed in to the water, to break the water tension in the soaker. Obviously, you'll need some plaster. I recommend dental plaster...this is a 50 lb box of the stuff. You'll also need some paper towels and spoons.
The white molds are mine. The larger stack of green molds are more Hirst Arts molds, and next to them are four 5" and 6" drywall knives, used to scrape the top of the molds to make all of the blocks and elements level and the same size. Sometimes we have all four drywall knives going, which means more molds being cast.
This is the demolding table, with two bits cabinets that hold 60 drawers each. On the table are several Hirst Arts casting elements that have recently been removed from their molds. Paper towel has been placed on the table, to protect the table from scratches and assist in drawing out any excess moisture that may be in the elements as they are being removed from the molds.
Here's the other end of the demolding table. I use old plastic berry containers to hold some of the larger or more frequently cast plaster elements. The smaller or less frequently cast elements are placed in the bits cabinets.
I have a lot of plaster elements previously cast and waiting to be brought together. Here are more berry and ziplock containers holding additional plaster bits.
The casting table is set up at the entrance to the garage. The pictured molds have been pre-soaked in the jet dry tub (the jet dry tends to break up the bubbles that form in the plaster and helps the plaster to flow into all the crevices of the molds) and are resting on paper towels that will soak up any excess moisture and unused plaster. The table has been covered with a black garbage bag to prevent stratches from the plaster and make cleanup easier. I get a lot of neighbourhood traffic dropping by to see what i'm doing, which gives me the opportunity to catch up on the latest gossip while i'm casting.
I half-fill the plastic cup with water. I know there is a specific ratio, but i'm too lazy to measure the water and plaster precisely, and this process is pretty old-hat now so I go mostly on feel.
I slowly add the plaster to the water until the cup is nearly full, usually only a 1/2 inch from the rim, and the plaster no longer absorbs into the water.
Here's the final product, after some vigorous stirring with a spoon, plus a little plaster on my hands.
The plaster mixture should be thick enough that it has the consistency of a thin milkshake.
Now it's time to pour. Some people spoon the mixture into the molds, but again, LAZY, I just pour the plaster directly from the cup. A little bit of splashing, but not bad. As you can see, on the right, the first mold is poured, and bubbles are starting to form on top, when trapped air has risen to the surface.
Nearly done the pour on the second mold.
And here are the first set of six molds, poured. The next step is vibrating the molds, so that any unreleased air bubbles can be released. I'll try to get to the next steps in a day or so.

8 comments:

Sean Robson said...

This is awesome! Thanks for the step-by-step pictures. I've been wanting to get some Hirst moulds for a long time, but I'm a little overwhelmed and unsure how to get started; this helps a lot.

Telecanter said...

Dang it, you're going to get me doing this. I love the fact that you can use the molds over and over and that you make what you need with your own hands.

christian said...

Great photos!

James said...

I'll confess (and apologise) that my question was actually about how much money you'd spent (and how much more you intended / needed to spend) but this step by step review of casting is just fascinating!

It all looks like a bit more effort than I generally have time, but I love the efficient method you've worked out.

Now I have another question (as well as the cost one): How do you make your own moulds?

biopunk said...

Yeah, yeah, yeah your molds and castings and tips for using surfactants are awesome and everything, but the question you are avoiding, the one we are all wondering about is really:

Which Canadian tunes are you listening to as you do this?

The right 'sonic vibrations' could further prevent the formation of bubbles, and bring increased joy to a legion of casters!

C'mon! Tell us!

Aaron E. Steele said...

@Sean: it really helps to find someone who is already familiar with the process. Will try to get to part two before the end of the week.

@Telecanter: the best part is making your own molds, once you become comfortable with the casting side.

@Christian: glad you liked!

@James: will get to the cost of molds, and the mold-making process. The mold-making process will have to wait til august, when I make some additional molds... I will do some photos of that process.

@biopunk: I just set my ipod to shuffle-mode, and let the awesome variety wash over the molds!

Bogus Gasman said...

Sweet! you got a regular old production line going there

chrissy bauman said...

Nice setup there. I just inherited some molds and am casting with stucco, it's not as nice as dental plaster but it sure is cheaper! I like what you're up to.