Casting Fine Trim Profiles
You can use Bondo, epoxy, or putty to cast a moulding profile you're trying to replicate. June 26, 2009
I am seeking suggestions of how to get a profile off the sticking of a window we are replicating. We tried the pin replicator that you push up against the profile and we tried tracing it on a piece of veneer and that did not give us enough detail. I have heard people using bondo but I don't know how to use it and I am afraid that I am going to hurt the finish of the existing window. Any suggestions?
(Architectural Woodworking Forum)
From contributor A:
Cover the piece with thin masking tape and bondo over the top or cover with thin plastic and bondo the shape.
From contributor B:
I have reproduced many historic architectural details and the pin replicator you describe is my first choice, although it is not cut and dry as you have found out. It provides a "base line" or rough shape for the profile. After transferring the shape with the wire gauge to paper I refine the accuracy of the profile or sketch by eye and measurement to the final shape. The result is very accurate, it just takes a little practice. I have never used bondo for this purpose although it is a good suggestion, I would use cling wrap or probably just some paste wax as a release agent instead of tape. Try a mock-up first to see how they will react. I also remember once talking my dentist out of some of the stuff they use to take impressions for crowns to capture a carving detail, that stuff works very well and then you can use it to cast a reproduction of the piece.
From contributor C:
The bondo trick works well. Start with 2" blue masking tape. Mask off 6". Make a couple of dams at each end out of tape. Cut a piece of wood 3/4 x 3/4 x 6". Mix up a big batch of bondo and mush the piece of wood into it. This will give you a little structure for your mold.
From contributor D:
Forget the bondo, use epoxy putty instead. Buy the epoxy putty that comes in a plastic tube. You knead it unti the color is uniform, then simply press it into place. I use plastic wrap to cover the molding, then roll out thin strings of the epoxy and press those into the details. Once the details are filled, I can apply the rest to back up the profile. The epoxy works better than bondo because you can use your fingers (wet them to prevent the putty from sticking to them) to make sure that the profile is filled. It also is much stiffer and does not run or need dams. It cures in about 20 minutes. The epoxy putty is also much cleaner and easier to use especially on site.
From contributor E:
Van Dykes has a two part putty that is mixed and pressed onto the detail you need. It sets in 5-10 minutes, peels right of, no damage at all or adherence to finish. It works for carving details also. I have done this often and cut off a portion into about 1/2" piece, sent to my knife grinder and had knives within a day or two. , about 20 bucks for a pint or so. Cant beat it.