Category Archives: Moldmaking

Middle Fork by John Grade


I saw this crazy piece by Sculptor John Grade on Colossal today and wanted to share it.

From Colossal:

Recently unveiled at the MadArt space in Seattle, Middle Fork is the lastest sculptural work by artist John Grade who worked with countless volunteers to realize this enormous scale mold of a 140-year-old tree.

The process began a year ago when Grade and a crew of assistants scaled a Western Hemlock tree in North Bend, Washington with help of a team of arborists. At nearly 90 feet in the air they created sectional plaster molds of the living tree which were carefully lowered and transported back to the MadArt space over a period of two weeks. Over the next 12 months, hundreds of volunteers (some who walked in right off the streets) helped to create a hollow sculpture of the tree using hundreds of thousands of small wood blocks. The final piece was carefully sanded down and is now suspended in the gallery. Watch the video below to see how it all came together.

Middle Fork is the first exhibition at the new MadArt space in Seattle and will be on view through April 25th before it goes on tour to galleries and art fairs around the U.S. In two years the pieces will be transported to the base of the living tree from which the mold was taken where they will decay and disintegrate back into the ground.



Images by John Grade from HERE

Waste Mold De-mold

Wanted to share some process shots of the demold I did on the waste mold from our NextFab Moldmaking Workshop. (I also made a video but am still trying to figure out how to upload it…)
The finished waste mold.
Chipping off the plaster I put on to cover the seam line.
Seam line uncovered!
Removing the wire binding the pieces together.
The underside of the waste mold. Because we used Hydrocal the mold and the casting are the same color. (I usually like to use Ultracal, which is grey and easier to see when demolding the piece.)
First piece removed. (I used a chisel to pop this off…not my fingers.)
I love when the pieces come off in large chunks!
The back of the piece demolded.
Normally we use cold chisels to demold waste molds but ours were at the studio and I was at home so I used this set of beater chisels. They, surprisingly, still have sharp edges so you have to be careful not to gouge your finished piece…or yourself…when using them!
The casting emerged successfully! Still needs some cleaning up and picking out of plaster mold bits, but it came out nicely.
The destroyed mold.

Silibrush test success!

All the rubber came off the Silibrush without tearing off all those little bristles. I’ll probably order a few more and test them by doing a paint on mold on something. I still won’t be 100% sold until I’ve done a paint on mold with them but so far I like where they’re going with this. If anyone else tries them, lemme know what you think.

Baby Rabbit Mold Finished!

After the rubber set up, I unclamped the mold and drilled some holes for bolting it back together later. I then removed the plaster mother mold pieces.
Here’s the rubber, which came out great!
 I trimmed off the excess around the flange and cut off the two vents.
Here’s the bottom before I trimmed it.
 Bottom of mold, post trim.
 Little man came out of the mold without his feet, 
but otherwise he was emotionally unscarred by the experience 😉
Time to clean out the mold. I soak it in warm water then scrub it with a chip brush and some Murphy’s oil soap to get the clay out.

Clean-ish…now for a test cast to get out the rest of the clay.
To cast it, I coated the inside of the plaster mother mold in Vaseline, placed the rubber back into it, foamed in some Murphy’s oil soap into the rubber mold as a mold release, then I leveled the mold….

 …and poured in the plaster…
…and in a little while got this guy! He came out really easily and I was really happy to be able to keep the rubber mold in one piece (once you cut the rubber, you get flashing along the seam lines that has to be finished in the plaster.) Once the piece dries fully, I’ll do the patina test.And then I’ll start cranking these guys out for our Kickstarter backers!

Mold continued…

So I poured the rubber into my mold yesterday and am eagerly awaiting when I get to open it (seriously, I am the most impatient person EVER…ask Justin.) I wanted to share some process photos in the meantime so here they are!
Here is the finished clay bunny…

And these are the mother mold pieces that go around him. I made sure to Vaseline the heck out of the mold pieces and the board that the sculpture is on, so the rubber won’t stick.

The rubber will fill in the spaces between the clay sculpture and the mother mold.

 I clamped the mold together and then clamped it to the board and modeling stand.

I then filled the bottom seam with clay to prevent rubber from leaking out.

 Ready to pour.

I used the clay that I took out of the mold (when demolding the plaster) to determine roughly how much rubber I should mix. I always add some to make up for any space that was between the clay and the sculpture.

New Rubber from Polytek! I’m using the 74-29 for this mold.

And a Silibrush…more later on how the rubber comes off of it…I’m dying to know!

I then got ready to pour my rubber…

Locked and loaded…

So I measured out the rubber, mixed it and poured it. I didn’t get photos of all that because I was too busy measuring, mixing and pouring (and I didn’t want to get rubber on my new phone…!)

As the rubber level rises in the mold it will eventually start to fill the other vent hole. As the rubber settled the level dropped a little, so I just refilled the holes to the top.


It’s always good when you estimate the perfect amount of rubber…
there was just a tiny amount left in the bottom…

Just enough to test out the Silibrush! (Will report back on how it went…)

Baby Rabbit continued…

I have been dying to start this mold, but since the rubber I had on hand didn’t fully set up, I had to order a new kit (The rubber I had was leftover from a commission I got in 2008 so it really didn’t owe anyone a thing…I was surprised it lasted as long as it did…) Because it hadn’t arrived before I left for the studio (sometimes Polytek’s turnaround time is ridiculously fast) I decided to do a blanket mold instead of a paint on mold. Below are some of the process photos.

  Baby bunny before the mold (I still have a few things to tweak before he’s fully finished, but like to do that after making the mother mold…just in case.)
I covered him with a thin sheet of plastic to protect him from the clay blanket.
This is me cutting slabs of clay to use for the blanket…which is not easy to do while simultaneously trying to take a photo.
Covering the rabbit with the slabs of clay.
Fully covered. (It looks like an ugly potato.)
Now for a flange around the bottom and a strip of clay along the length of the piece.
And 2 pieces of clay that will end up as a pour hole and a vent. 
I then added some metal shims along that key that runs the length of the piece so I could do both sides of the mother mold at once. I Vaselined the board and the shims and then mixed up some plaster, threw on a splash coat and then one layer of burlap. I thickened up the edges so I’d have something to bolt through. Because I did this in about 12 minutes (I was running late to pick up Justin for a meeting at our new space!) and had plaster on my hands, I didn’t get any photos of me making the mother mold.
After our meeting at the new space, we stopped at Rocket Cat for some coffee (and an apple for O’Rae). Then back to work.
I pulled out the metal shims…
…then carefully removed the first side of the mold…then the other.
He survived!
I cleaned out the clay from the inside of the mother mold, placing it all in a multi mix bucket to measure roughly how much rubber I’ll need to pour into the mother mold.
I then cleaned up the edges a bit and put it back together. 
Once the rubber arrives, I’ll finish the mold, so stay tuned for Part II!

SiliBrush or Silly Brush?

Has anyone seen these yet? This is a Silibrush by Polytek. Here’s a bit more info from their website:

New reusable brushes save $ when making brushed molds. They are 6.5″ long and are made of silicone so they can be used to brush polyurethane rubbers and plastics. Once the polyurethane cures, just peel it away from the brush and it’s ready to use again. We recommend having 4 or 5 brushes on hand so a new one can be used for each coat of rubber applied (eliminates having to wait for the rubber to cure to be removed). Our tests have shown these brushes work with TinSil and PlatSil products as well. Test them out for yourself. 

Now I have to admit, I am intrigued, but skeptical. I love Polytek but I can’t tell if these are genius or would be awful. When making rubber molds, we go through a ton of chip brushes and I always feel guilty creating so much waste…I’d love to find a way to use less brushes but I wonder if this would do the trick? At $5.00 each vs. $6.99 for a 36 pack of chip brushes, the price is a bit steep…and I wonder if those little silicone fingers would just tear off when peeling away the polyurethane. Hmmm…I’m about to place an order with Polytek for some new mold rubber (the stuff I tested the other day never fully set up so its no good…) and might just get one to try it our and report back…The crazy things we do in the name of research…!

Moldmaking and Beer go together like Peanut Butter and Jelly

No, this is not a Philadelphia Brewing Company ad (though it could be…sculptors love beer, right?!) Before Justin started making a waste mold for a student of mine last night, the big question was not “metal shims or clay walls?” (we’ve done both in the past and are going through a metal shims phase again at the moment) or “casting in Hydrocal or Ultracal?” (the client wants Hydrocal)…it was “What kind of beer should I get?”…(We decided on the mixed case from Philadelphia Brewing Company…yay for local breweries!) And when I asked him to take photos of the piece during the process, this glass of Kenzinger somehow snuck into the frame, which made me laugh. Neither of us drink much, or often, but there is something about making molds that doesn’t quite feel right without a cold beer in hand at the end. Cheers to that!

To any non-drinking readers, our apologies if this seems one-sided. We don’t want anyone to feel left out. If no beer is available, ice cream has been known to produce a similar feeling of contentment post-mold making. For me, a Chipwhich in particular…Enjoy your after mold making delights…whatever they may be!