How to replicate antique wood moldings

We haven't written much on "home improvement" lately, mainly because there hasn't been anything to say that would be remotely helpful. But I just finished a project that probably fits the bill: duplicating antique wood carvings (or plaster, for that matter).

Our house was missing two pieces of an ornate carving when we moved in. It'd be all-but-impossible to find an identical replacement, short of stealing one from a neighbor. So I called Van Dyke's Restorers and asked if they sold anything I could use to create a mold. Yes. Yes, they did.

I needed two products: Silputty, which allows you to make a (negative) mold of the wood piece. And Por-A-Kast, the stuff you pour into the mold to make a (positive) replica.

MAKING THE MOLD

Step one is to clean the original piece, removing any dust or debris. Next, you coat it with cooking oil or vaseline (spray oil is easiest) so that the molding agent doesn't stick to it. Silputty consists of two clay-like balls that you need to mix together quickly because it cures in a matter of minutes. We needed two kits in order to make a mold large enough for our piece, so I enlisted Charles' help. We put on rubber gloves and each started mixing a kit at the same time. Doing so was harder than I thought - I'm a weakling - so as I soon as Charles finished mixing his batch, I handed him mine to finish, then we combined the two and stretched the green blob out onto a greased sheet of glass (any flat surface will do). Kinda like making pizza dough. As soon as we had it stretched to the right size, I pressed the wood piece into it and left it there to cure.

Thirty minutes later, we had our mold.

MAKING YOUR DUPES

The next part is a bit trickier. Por-A-Cast is highly toxic, so it's best to do this outside when the weather isn't terribly cold or wet. (Moisture and cold air will prevent the materials from setting properly.)

The Por-A-Cast kit comes with two cans of chemicals. Your task is to blend the stuff in can A with can B at precisely the same quantities, stir gently but quickly, then pour the mixture into the mold. Be sure to place a cheap dropcloth or lots of newspapers under the mold so you don't spill the stuff on your stoop like I did.

For mixing, I used translucent plastic cups with little ridges (above right); those ridges made it easy to measure the precise quantities. Once I had what looked like identical amounts of liquids, I poured them together into a larger plastic cup and mixed with some disposable chopsticks (plastic silverware is also good).

The first time I did it, I mixed too long and the junk set while it was still in the cup. Fortunately, there was more than enough liquid to make multiple batches, so I tried again, spent less time on mixing, and it worked. I left the stuff outside for a few hours to cure, then kept making more replicas until the agents ran out.

So then I had a bunch of plastic-y, white molds with various imperfections. To shape up my models, I used a Swiss Army knife to whittle down edges and places where Por-A-Cast wasn't supposed to go. This was easy. Like whittling soap. I needed only two replicas, but I made a couple of extras in case one broke (which one did—I didn't put it securely in place and it fell and broke).

COLORING

I painted a coat of primer over the molds so that paint would adhere to them. Next, I had to figure out how to match the color of the original woodwork. It was finished with shellac and therefore had a warm, amber patina. Like any varnished woodwork, the color wasn't solid: it was a mix of dark brown and amber highlights. So I selected a paint color that most closely matched the underlying orange tone, then painted a coat of that over the primer. The results are shown here.

Next, I brought out my gel stain: a mix of Bartley's maple and dark oak, which magically seems to match all of the woodwork in our house. Gel stain is thicker than conventional stains and goes on more like paint. It is usually rubbed off like a typical stain, but in this case I simply painted a think layer of it over the orange and let it dry.

The resulting color blend was a pretty dead-on match. No one would mistake the piece for wood when holding it in hand, but it's hard to distinguish otherwise, particularly when placed in position overhead. Even yours truly—who usually fixates on the flaws in the woodwork I've refinished—can't tell the difference. But, just to be sure, I moved one of the original carvings next to the other original, and put both fakes next to each other to minimize any distinction. In the photo here, both bottom pieces are replicas, whereas the smaller carvings above are original. Pretty cool, huh?

Note that I only bothered to replicate the molding on one side. The back side is a fairly straight plane, but with the paint and the stain you can't really tell because of the lighting in this room. (When looking up at the moldings from the other side, they're either backlit from the sunlight and silouetted... or the light is too dark to see the fine details anyway.) If I were more ambitious, I could have made molds of both sides of the carving, glued them together, and caulked the edges before painting and staining, but there's only so much time in the day...

Comments

[dt]

Very cool! Where did you buy the gel stain?

[carrie]

By mail order from Homestead Finishing. I linked to the web page above (see "Bartley's"). You have to call or fax them to place the order, though. They're pretty old-school.

[tomg]

Thank you for this post!!
I had asked you about the process before, but this makes it very clear. I tried to make a mold with soft clay and it was not good. The problem I had was not getting the back side flat and I came out with a wavy mold. I will try Silputty and see if it works better.
I didnt know that the Por-o-cast was so toxic (the smell is awful). I found art supply stores have casting chemicals as well.