window sash repair

[DWM]

I am in the process of restoring the original windows in a turn of the century farmhouse in Fayetteville Texas. I am having some difficulty in repairing the muntins as they are very thin. Any advise you could offer on how to do this would be greatly appreciated.

[Paul Marlowe]

To begin, safely remove most or all the paint down to bare wood, at least in the damaged area. 

1. My first choice for a technique would be to brush consolidant on the the damaged wood as needed, then apply the patch by packing the voids with a small plastic putty knife.  Follow that with a sharp plastic putty knife just wide enough to span the damage and carefully place it parallel with the muntin profile.  Move the knife over the area trying to leave just enough patch to fill the voids.  Let it cure, then plane, scrape and or sand the area.  Touch up with another coat of patch alone, but only if needed to create more detail. 

FYI: Metal putty knives can also be used.  Either type can be wiped with paper towel when finished and set aside so any remaining epoxy can cure.  Once cured you can scrape or sand any remaining epoxy to help maintain the crisp edge of the knives.  If taken care of they can be used over and over for years.

2. You can create the shape of the profile on the end of a thin stick by coping the end to the muntin.  This stick can then be used to tool the wet patch and match the exact shape desired.

3. Another method is to make the coped shape with 200 patch.  To do this apply a thin film of wax on a perfectly shaped, bare (free of paint) portion of the muntin profile.  Cut a thin stick approx. 1/8" + or - and a few inches in length.  The width should be at least equal to the height of the muntin, stile or rail profile being repaired.  Set the stick perpendicular to to the profile and cut a straight sloping angle or roughly scribe the end to the profile.  Apply patch to the end and brace it against the profile which is coated with a thin film of wax and let it fully cure.  Remove, sand the sides and use this to tool the wet patch along the damaged profile the same as described in #2.  Remove the wax from the muntin profile before painting.

FYI: A few release agent options for epoxy are butchers wax (paste wax), clear wrap, polyethylene and wax paper.