Thread: alternative pore filler for hard shellac

Originally Posted by Heartstrings

I`m finishing a guitar that I originally planned to finish in hard shellac, the only filler I`ve used so far for french polishing is pumice but when I started to make up some samples the pressure from the pumicing made my shoulder ache like crazy. The instructions that came with the shellac said to use a coat of regular shellac on raw timber then use the hard shellac for the rest. I thought I might try to use oil based clear filler over that first coat, sand back when dry, apply another coat of regular shellac then switch to the hard shellac. Has anybody tried that or can someone offer another alternative to pumice, that is transparent. I`m using a piece of spalted pecan for the top of the guitar and don`t want anything but the color of the wood showing. Thanks Mike

When I French Polish I use plain Plaster of Paris mixed with water, sometimes if I want it dried in a hurry I'll mix it with Metho,, rub it in allow to dry. Rub off excess rub in Raw linseed Oil, it goes transparent, allow to dry. Put the shellac over the top of that. That's the method that's been used for 100's of years. I think instead of Plaster of Paris they may have used Arrowroot. Same effect thought.


Cheers


Steve

Originally Posted by toolbagsPLUS

When I French Polish I use plain Plaster of Paris mixed with water, sometimes if I want it dried in a hurry I'll mix it with Metho,, rub it in allow to dry. Rub off excess rub in Raw linseed Oil, it goes transparent, allow to dry. Put the shellac over the top of that. That's the method that's been used for 100's of years. I think instead of Plaster of Paris they may have used Arrowroot. Same effect thought.


Cheers


Steve

I`ve heard of plaster of paris used as a pore filler but didn`t realize it would go transparent by applying the linseed oil. That sounds sounds much easier than anything I`ve tried. I notice you said raw linseed oil, will boiled work also? I tried to find some raw oil a few years back at the local hardwares,no luck, if it does have to be raw oil I`ll have to get some online. Thanks for the advice, gonna give it a go. Mike

Mike, try the chemist shop for raw linseed oil, here in Australia you can buy it from chemist's
Cheers,Bob

Originally Posted by Heartstrings

I`ve heard of plaster of paris used as a pore filler but didn`t realize it would go transparent by applying the linseed oil. That sounds sounds much easier than anything I`ve tried. I notice you said raw linseed oil, will boiled work also? I tried to find some raw oil a few years back at the local hardwares,no luck, if it does have to be raw oil I`ll have to get some online. Thanks for the advice, gonna give it a go. Mike

pumice is mainly silica i think - or feldspar which is mainly silica

AFAIK silica is used as a filler in sanding sealers
you can by <400 mesh industrial grade silica at any ceramics supply place dirt cheap
eg potters equipment in ringwood [melb]

i would imagine it would be ok in shellac - will save yer shoulders and definitely worth a few dollars to try a test

I remember seeing a post from Neil which said that you can also use talc mixed in with the shellac.

talc is magnesium silicate & again it is mostly silica and can be purchased cheaply from the above ceramics supply house

Originally Posted by Heartstrings

I`ve heard of plaster of paris used as a pore filler but didn`t realize it would go transparent by applying the linseed oil. That sounds sounds much easier than anything I`ve tried. I notice you said raw linseed oil, will boiled work also? I tried to find some raw oil a few years back at the local hardwares,no luck, if it does have to be raw oil I`ll have to get some online. Thanks for the advice, gonna give it a go. Mike

HI Mike,

Apparently not as it has a drying agent mix with it. Raw linseed can be bought from Hardware Stores or Produce stores or any Horse outlet, it is often fed to horses to increase the gloss on their coats.

Cheers

Steve

Originally Posted by TP1

I remember seeing a post from Neil which said that you can also use talc mixed in with the shellac.

You use the talc in your rubber as an abrasive as well as a filler. Works well.

Gonna try both methods and see witch one is going to be easiest on my joints, located the plaster at an arts and crafts store but will have to get the oil and talc online. Thanks for the advice as I haven`t had much of a need for pore filling till I started building guitars. Joint compound works really well but has to be tinted, clear is what I`m after here and I`ll give a reply when I`ve done some test samples Mike

Just don't use 'talcum powder' from the supermarket as it is not really talc or pure talc anyway. Check out Google books for some really old (and knowledgable sounding) texts on finishing. They are detailed and discuss all of this sort of stuff. They are also free!

Let us know how you go.

See for example:

French Polishing and Enamelling by Richard Bitmead - Project Gutenberg

=Filling-in.=--The first process the wood usually undergoes is
"filling-in." This consists in rubbing into the pores of the wood
Russian tallow and plaster of Paris, which have been previously heated
and mixed together so as to form a thick paste. For rosewood, or to
darken mahogany, a little rose-pink should be added. After well rubbing
in, the surface should be cleared from all the surplus paste with the
end of the scraper, and then rubbed off with shavings or old rags, and
made quite clean. For birch or oak, some use whiting or soft putty
moistened with linseed-oil for the filling; this preparation prevents in
a great measure the rising of the grain. For white delicate woods, such
as sycamore, maple, or satin-wood, plaster of Paris, mixed with
methylated spirit, is used. When polishing pine, a coat of Young's
patent size (2d. per lb.) is used instead of the above mixtures, and
when dry is rubbed down with fine glass-paper.

Some workmen, who regard their modes of filling-in as important secrets,
do their work surprisingly quick by the methods here given. The various
processes are soon acquired by a little practice, and contribute greatly
to the speedy advancement of a smooth and imporous ground, which is the
most important point to observe in polishing.

I french polish my acoustics. Comments on grain filling:

1. I currently use the pumice method or use egg whites. An egg white wash is also handy for sizing furry top woods such as Englemann spruce.

2. Epoxy resin can be used as an effective pore filler and is a method that involves minimal physical exertion. I was using Zpoxy finishing resin for a while but I now prefer the methods above as they involve less hazardous materials.

Cheers Martin

Originally Posted by old_picker

pumice is mainly silica i think - or feldspar which is mainly silica

Pumice is predominantly quartz (essentially SiO2). Felspar is a silicate with the different varieties of felspar forming a solid solution series between Sodium and Calcium rich end members.

See this thread for more discussion on pore filling:

https://www.woodworkforums.com/f9/pumice-stone-112754/