Got lucky and saw my neighbor putting two chairs out to the street. One was this grey chair. In really good shape, with some wear around the edges and the white paint splatter that comes from being kept in the garage.
Having never really taken a close look at one of these fiberglass chairs, I was surprised that the fibers are completely visible. It’s a really honest approach, and the fibers give the chair a texture that it wouldn’t have with a uniform gel coat. The earliest chairs are said to be translucent, which is pretty cool and must have really blown people away at the time.
Seeing the fibers made me want to replicate one in fiber-reinforced concrete. It will have to be thicker, about 3/8″ (the fiberglass chairs are only about 1/8″ thick). The downside with a concrete version is that it won’t flex like fiberglass, which is part of what makes the original so comfortable. Also those crisp edges are going to disappear, and making the back side look good will be a challenge.
The mold is made with a type of plaster (Hydrocal FGR-95) designed to be used with glass fiber mat. This is a very strong plaster, sometimes used by archaeologists when they need to transport dinosaur bones from the field to the museum. It’s also used by sculptors and model makers to create exterior support shells for rubber molds. It’s also used in similar ways to GFRC, to make wall panels, fireplace surrounds, interior trim, stuff like that – for commercial, residential, and stage sets. The best references I could find for using FGR-95 are from the USG website: Casting Fireplace Surrounds PDF , and this PDF detailing how to make cases for turtle shell specimens from the journal of paleoantological techniques. I got the plaster locally at Douglas and Sturgess, and they’re always really helpful when it comes to answering questions about this kind of stuff.
The thing that really worried me before doing this is that I might get the chair stuck in plaster, or damage it when trying to get it out of the mold. The point here is just to see if I make a nice concrete copy. Let’s not to pretend a concrete eames chair could be any better than the original.
Elephant Hide Grey, H-Base, narrow mount, Side Shell, from the 70s. Herman Miller Stamp and the C with the Star indicates it was made in Cincinatti Milacron. On the decal are patent numbers, searching them on patents.google.com has been fun. Half the label tore off while I was cleaning it after these pictures.
The first thing to do is clean the interior of the chair, and then protect it from the casting that’s about to take place. Gel-Gloss is a cleaner and polish for fiberglass and acrylic, it’s rubbed into the surface and buffed off with a clean towel.
I applied multiple coats of gel-gloss, around the entire seat area, and just around the edges on the back side.
For the plaster to release, the thing needs to be as smooth as possible. A few coats of mold release wax was applied and buffed off.
The back and legs of the chair are taped off to keep them clean. This is an important precaution, especially if you’re messy like me, because plaster will get everywhere.
The first coat is a hand lay-up coat of plaster slurry (20-25 parts water : 100 parts plaster – no fiber mat on this coat). The first batch of 5 lbs. was enough to thinly cover the chair and edges, about 1/8″ thick or a bit more.
The water is weighed out and added to a bowl, and then plaster is dumped, forming an island in the middle. Let it soak for a few minutes and then mix it up. It will be runny at first, but after 5-10 minutes it should lay-up easily. The working time is something like 30 minutes, but at some point it starts to set up quick.
The face coat laid up easily enough, and I let it set for 45 minutes before starting the next one.
The fiber mat is cut into strips, dipped in plaster, and applied to the form. The mat can be peeled apart, making it thinner, and I should have done this on the first coat, because the weight of the plaster-soaked-strips caused the face coat to slide down on the tall vertical surface.
Each coat coat took about 6 pounds of plaster and enough 3″ wide strips of fiber to cover it completely. The plaster wasn’t touching the sides completely, so I wrapped fiber around the chair to help them make contact (like wrapping a mummy).
Apply more coats until the thickness is about 3/8″+. I waited an hour or two before trimming the edges. Trimming is easier when the plaster still has moisture in it, and it can be done with scissors or a knife. I waited so long that it needed to be sawed off, which was a pain in the ass, but I wanted to make sure the plaster cast wouldn’t get messed up by cutting into it.
The way I did this is very tedious, so I recommend trimming as often as possible before the plaster has time to harden.
I used a small saw to make a control just above the edge of the chair, then cut away from the side and removed it chunk by chunk.
With most of the excess removed, the rest can be sanded down with an orbital and very rough sand paper (40 grit). This is now the next day, sanding outside instead of in the kitchen…
A coarse rasp or a small hand plane can also be used to shave down the plaster, but it was a lot quicker with the orbital. Wear a particle mask, and your dirtiest clothes, and long sleeves if you don’t want to itch.
At some point the tape can be removed, this helps expose the edge of the chair so you can see where to sand down to. Be careful not to go too deep and sand down into the chair.
I used a razor blade to chip and cut away the last bit of plaster. When it’s so thin, it will break away easily. Going all the way around the edge takes time, but you’ve gotta do it if you want to get the chair out.
Blowing compressed air between the chair and the form will break the seal and help the chair release. I used wood wedges to force the chair up at the loosest points. Then after blowing more air down the edge, it was free!
The casting isn’t too bad. There are some holes to fill, and it’s rough where the plaster slumped down, and some fiber is showing through the face coat. The texture of the original chair is visible in the plaster, which would show up in the concrete piece, but because of the spot repairs, the whole thing will be sanded down smooth.
The residue on the chair shows where the plaster slumped down. All of this buffed off and aside from a few scratches on the edges, no real damage was done to the shell.
I started filling the larger holes with the same plaster. Fill, sand, fill, sand, fill, sand. It would take less time to just make another, better casting, but I wanted to work with what I had.
Then I moved on to filling the last holes and low spots with bondo. Fill, sand, fill, sand, fill, sand, fill, sand. Very time consuming. Sanding is done with a block and by hand using 80 grit paper and working up. I only went up to 220, but there are were still some fine scratches. Hopefully they’ll be filled in with the wax in the next step. All of the original texture from the chair is gone at this point.
Filling and sanding done, after at least 6 hours and 3 beers.
Last week I left the mold in the sun every day to help it dry out. If the plaster still has moisture in it, it will cause problems when casting. Sealing the plaster is incredibly important. I’m using a mold release wax, but it could also be painted or varnished.
Apply the wax, buff it off, and do it multiple times (4 to be safe).
The last step before casting is to spray the whole thing down with mold release. Now it’s very smooth and slippery, which is good, but also bad because I’m going to hand lay-up the concrete, so it will want to slide down and slump.
Finally, with the mold making finished, it’s time to cast concrete.