FILLING OAK
A very good hardwood filler for oak, either for a natural or golden effect, may be made from two parts of turpentine and one part of raw
linseed oil, with a small amount of good japan* to dry in the usual time. To this liquid add bolted gilder's whiting** to form a suitable paste, it
may be made thin enough for use, if to be used at once, or into a stiff paste for future use, when it can be thinned down for use, says
Woodworkers' Review. After applying a coat of filler, let stand until it turns gray, which requires about 20 minutes, depending upon the amount
of japan in the filler, when it should be rubbed off with cotton waste or whatever you use for the purpose. A filler must be rubbed well into
the wood, the surplus only being removed. The application of a coat of burnt umber stain to the wood before filling is in order, which will
darken the wood to the proper depth if you rub off the surplus, showing the grain and giving a golden oak effect. The filling should stand at least a day and night before applying shellac and varnish.
* 'Japan' generally refers to a broad range of hard lacquers similar to Chinese porcelain. I am not sure which particular product the author may have been referring to, but there are many great products available today. - Webmaster, Informationclickdepot.com
** More commonly seen as Gilder's Bolted Whiting. It is a grade of whiting popular with picture frame makers.