Category Archives: Sculpting Progress

Progess updates of what I’m working on now

Parting line

I added vents at the ends of the arms. They are cocktail straws, snipped and buried halfway in the clay bed.

At last I’ll finalize the parting line around the piece for the mold halves. Prepare a variety of clay snakes, collect your favorite tools, and find a comfortable place to work with good lighting:

Also, have a good cup of coffee, and listen to Radio La 2×4 Buenos Aries. (http://www.buenosaires.gob.ar/la2x4)

The techniques I think works best is, having built up in a general way close to the piece, to now lay a line of clay along the remaining gap of about the same size as the gap or slightly larger, and simply press it gently into place with small tools.

This neatly fills and seals the gap, without applying pressure onto the piece which will make the clay line difficult to remove cleanly and without blemish to the piece later. The gap must seal completely.

One side done, halfway around.

And finished, including some keys which can help to keep the two halves in alignment. I don’t take keys too seriously like some people. I think the complexity of the plaster mother mold’s shape, is enough to keep the silicone in place, but people expect to see these in a mold so do a little of it, for example. I think channel shaped keys like this do more to help prevent material you pour into the mold, like wax or plastic, from leaking out at the seams while it solidifies.

Next, I’m ready to pour the silicone to form the blanket mold of the first side you see here. Exciting!

Filling

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I’m filling in the five holes which are on the center axis of the figure. This is just parting line on the interior of the figure. Not much to look at really, but these details are for my own notes.

I’m depending on having made the silicone blanket thin enough to peel-back, pinch-away from, extract, the mass of these plugged holes from the narrow V-shaped crevice they are in. If not, I’m still confident that the silicone will peel off with only some amount to damage to the wax, which I will eventually pour into this mold, in which case , I’ll repair the wax by hand before making the bronze from it. No big.

Open

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I had to go snowboarding again, sun and snow perfect, clear-minded oblivion. By now the plaster shell is really dry. I stand it up and very carefully, open it by inserting some wooden wedges and tap gently with a hammer. As soon as the suction is broken it comes apart easily. Do not pry. Be patient. I open the mold so as to reveal the first side that I worked on, that hasn’t seen daylight since the end of December. Nice, isn’t it? Face it, there is satisfaction in doing your craft right.

Now I’m going to remove that pretty clay blanket and reveal the model under it. I’ll use a palette knife to cut and separate the blanket from the plaster,

carefully peal back the blanket,

more,

and more, until the model is revealed, but still resting in the bed of clay which is the second-side blanket. I had done some work earlier on to roughly define a parting line in clay from this first side, when it was still in the cradle, and you can see some of that in place still. The task now is to detail that parting line perfectly.

I save the clay blanket that was removed, because I can weigh it and know roughly the amount of silicone rubber I’ll need later to fill the void between where the blanket was removed and the plaster mother mold. We’re some way off from that still.

I cut back the plastic wrap with small scissors, which has been helping to protect the model from the clay blanket to the existing rough parting line,

and tuck in the loose edges under the rough parting line. This way the plastic is still protecting the second side, you don’t need to remove the model from the mold at all, to get the plastic off, and it’s usually hard to do that without harming the model anyway.

There we are, ready to begin work on the final parting line. I’ll point out that the outlines will be pretty simple, but the holes through the middle of the body must be handled somehow and even though the silicone rubber material is very forgiving about undercuts and such, I’ll need to proceed with deliberation and reason.

Shell fini

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The box removed, and the plaster shell mold smoothed.

I’ll just let it cure, dry, and harden up a little longer, so when I split the two half apart, very gently, I won’t crack either half. The clay underneath undulates a lot, so removing the shells evenly, in one piece, using small wooden wedges, will be a trick.

Meanwhile, on the side, to use up the free time, I cast the Beachstones molds I made last Fall in urethane resin. (The waxes I made earlier from these molds for bronze didn’t work out too well and I’m going to do them over, soon I hope.)

It still needs finishing, but I’m very please with the way it turned out – that’s saying it came out looking like I’d hoped – like beach-glass, you know, that sand-smoothed broken glass you find at the beach. Look forward to more.

Back plaster

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I boxed up the mold, preparing to pour the plaster for the back side. I just build this quickly using foam-core, hot glue, and tape, lots of tape. I seal the inner seam of the box with clay where it meets the front side plaster so there is no leaking out of the new plaster. I line the inner side of the box with packing tape to release the plaster. I added the sprue and vents for the silicone to eventually pour into, in the form of cardboard tubes and soda and cocktail straws, but that step is still a way off (the clay under the plaster will be removed and replaced with poured-in silicone, forming an inner blanket which is supported by the solid plaster outer mold). It’s a lot of details with not much to picture.

Mix the plaster, something I’m not showing you, pour it on and shape it up. You can see some markings above which I use to estimate the thickness I want from the plaster.

I’ll let this dry a few days, take away the box and smooth it out some more.

It is a relief to be at this point. I’m maybe halfway done, but some of the most critical planning and preparation steps are complete now, and if I’ve done this correctly, most of what follows will be clean straight-forward work without anxiety.

Back blanket

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It’s been a while. Went snowboarding in Wyoming with my brother-in-law, his wife & my remarkable niece. What fine hosts, and I had the greatest time there. I’d been to the Tetons many times in the summer to hike and climb, but this was my first time there in winter to snowboard. An excellent variety of terrain, rugged and scenic. I miss those days when I would lose myself in nature & the dissolution of the self, but after being so out of my head there and on return, I and ready to get back to work on this. The few people following this blog have told be they have in fact no complete idea what the process is here I’m illustrating; and how I can focus so much seeming effort upon it?

It is the complexity of it all which lets me lose myself in the work.

Here’s the first side again, now trimmed back from the edges to expose the plaster surface and match the extent of the first side blanket, which of course you can’t see, so it’s helpful to have pictures to refer back to. The new second plaster side will match face-to-face with the exposed plaster, creating a shell, or mother mold, within which the silicone mold is supported.

Another clay blanket is made now for this, the back side of the model. Again, these are sheets of clay not more than 3/8th inch thick, laid on the model.

After a rudimentary smoothing-out. This layer will become the shape of the silicone mold rubber to eventually take its place, and the second side plaster will be poured on top of it, so it must not have any undercuts to interlock with the plaster.

The nearly final form of the blanket.

Next, I create the sprues and vents for where the silicone will (eventually) pour in, and box it up all around (again) so the plaster can be poured on.

Front plaster

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Mold release is liberally applied to the clay and insides of the box. I use a aerosol spray-on product made from halogenated hydrocarbons in ether, well-worth the money for it’s effectiveness and ease of use. The plaster is poured, shaped and formed over the clay blanket. Doing this deserves some more photos, but I am too involved to stop and take them. Mixing plaster and applying it is a skill I have only begun to get at all proficient. This is about 1.5 to 2 inches thick, about right, could be thinner.

Removing the foamcore box, I trim and smooth out the plaster with a palette knife. It is mostly pointless, but I can reduced the volume of the plaster shell a little, and anyway, it makes it look nice and feel better to handle.

Now it should cure for least several days to a week. The plaster continues to dry out and get stronger. I want to wait to separate the assembled three layers- plaster, clay blanket, and model, from the cradle, which will be the next step. Removing the cradle will put pressure on the plaster and I want to be sure it is as strong as it needs to be so it doesn’t crack.

Front boxed

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Here I’ve boxed in the front half, preparatory to pouring the plaster mother mold half. It includes a pour sprue and vents at all the high spots.

It’s made from foam core, hot glue and packing tape. I think this is a way to work faster, and have a smaller plaster mold to deal with. I have usually made these boxes from wood, but this is easier to fit to the shape of the model. I hope it will be strong enough to support the weight of the liquid plaster. The inner surface of the foam core is lined with packing tape, and the whole clay surface will be sprayed with mold release before the plaster goes on.

Vents must release the air from the mold at every high spot, or the poured liquid silicone will not be able to fill the mold entirely. I may still add a second sprue; While the silicone is forgivingly self-leveling, this mold has so much topography that it may be helpful. I can also thin the silicone to help it flow more smoothly.

matthew DG

Whatever I'm doing & sculpture

Category Archives: Sculpting Progress

Parting line

Filling

Open

Shell fini

Back plaster

Back blanket

Front plaster

Front boxed