Uses of putty and bleaching when staining

RESOURCES

Plaster of Paris Putty

is used by some finishers on new wood to be finished in the natural color or stained. This putty will absorb stain and the color given by fillers. The plaster of Paris putty is made by simply submerging a handful of dry plaster of Paris in water. As long as it remains below the surface of the water it will not set, A small amount should be lifted with the putty knife and kneaded with the fingers. Press it into place and clean off the surface around it. Be sure to fill the cracks and holes full and level with the surrounding surface.

Cabinet Makers' Putty

is made of fine wood sawdust from the kind of
wood to be filled. The dry sawdust is mixed with a glue made from 1
ounce of good quality glue and 16 ounces of water. A little water color
or dry pigment tinting color is added if needed to make the putty
match the surface. When this putty is well made and used it is
practically impossible to detect the fillings, even in fine woods like
mahogany and walnut

The wood finisher has occasion to use bleaching solutions for the
purpose of removing stains from woods to be finished or refinished,
such as rust stains, water and weather stains. He also needs a
bleaching solution occasionally to bleach large surfaces of maple,
birch, oak, walnut and other woods which are to be finished in as light
a color as possible, for instance, oak, which is to be finished with one
of the popular light gray, two-tone finishes with white filler, and walnut
or gum, which are to be finished with the very light brown French
walnut color. Then again when old stained and varnished surfaces are
stripped off, removing all the old finish possible the wood is sometimes
found to be too dark to take the new stain of light color and make a
nice job.

The bleaching processes use water solutions and they raise the grain
of the wood. So after the bleaching and neutralizing washes, the
surface is permitted to dry and is then sandpapered to cut off the
raised wood fibres. Sometimes a very thin coat of white shellac is
brushed on to make the wood fibres stiff so they can be sanded off
easily with the sandpaper.

After bleaching the surface may contain a bit of the chemicals and it is
a good idea to wash up immediately with clean water, using a
sponge. Then a coat of ordinary table vinegar without dilution will
neutralize any alkaline traces left on the surface and make it safe for
finishing coats. The surface should be allowed to dry at least twelve
hours before the finishing coats are put on.

There are many chemical solutions used for bleaching. Some are most
effective on one wood while others succeed best for other woods. The
oxalic acid solutions are probably used most by wood finishers in the
house building industry.

Before using any bleaching solution it is best to thoroughly clean and
scrub a surface, using hot water to which soap and a little sal soda
have been added. Use a wad of No. 2 or No. 3 steel wool for the
scrubbing, then wash up well with clean water, using a sponge for this
purpose.

Oxalic Acid Bleach.

Oxalic acid can be secured from any drug store or paint stores in a dry crystal form. Usually a saturated solution is made by dissolving as much of the acid crystals in a gallon of water as the water will take up. Hot water is best and the solution is more effective when put on to the surface to be bleached while it is very hot. Use a old flat wall brush to apply the solution and let it dry on the surface. For bleaching weather stains and also dark sap streaks in wood, 8 ounces of oxalic acid in two quarts of water is about right.

If the first application of bleach does not remove the discolorations or
make the whole surface as light as you want it, apply the same
solution hot a second time or repeat several times. When sap streaks or
whole surfaces to be bleached are greasy, wipe them off by rubbing with
denatured alcohol and let dry before the bleaching solution is put on.

Chlorine Bleach

makes an effective bleach, especially if it is followed by a solution of hydrogen peroxide . Use this bleaching solution hot and brush it on
with an old flat wall brush; let dry; wash up with clear water.

Hydrogen Peroxide Bleach.

This chemical is a positive acting bleach when freshly made. It is a little expensive when large quantities are needed for large areas of surface. For small stains on patches and spots it is entirely practical. Brush on and allow to dry. Wash up with clear water.