On one of his videos, Robert O'Brien recomends using tinted drywall compound to fill the grain in guitars.
This would be very attractive as living in Trinidad it is hard to get some items and impossible to ship others.
I also like to find out the base recipies for common products we use every day, and third I'm trying to source as much as I can locally to build guitars.
does anyone have any insight on this application?
Dry wall compound does indeed work and so too will a plethora of other things as well. The folks who I know who have used dry wall compound, including Robbie O'Brien also tint the stuff prior to use.
Personally I prefer epoxy and when I am speaking of epoxy what I mean are quality epoxies such as System III, West Systems, and Z-Poxy. With Z-Poxy the "finishing resin" is what has worked very well for me personally although I have also used West Systems and SIII with great results.
Pore filler is nothing more than, well, something to fill the pores with that will stay in place during the finishing process, is easy to get in the pores and level, and resists to the greatest degree possible shrinking back over time. Some pore fillers such as epoxy are pretty good at "popping" the figure on figured woods and can be used to tint or darken the instrument's appearance too.
Nice thing about dry wall compound though is that many of us have that 5 gallon bucket of the stuff, half used some years ago, laying around.
As a boat builder I use a lot of epoxy, one thing I like to do is coat wood with epoxy prior to varnish,
it bonds better to wood than varnish and leaves an inert plastic base, the wood is stabilized against humidity based swelling & shrinking
one coat of epoxy fills grain about equal to five +- coats of varnish, so the process is speeded up
downside ,you still have to put on enough coats of uv varnish to protect the epoxy from the sun
and germain to this post it darkens the wood considerably. to the point that many owners think it is too muddy
also if you sand through you never quite seem to get rid of the splotchy color differences
Hesh do you notice this when you fill pores with resin?
if a heavy coat of poly varnish changes tone does epoxy do this also
my thanks to everyone who answered this question
In George Frank's book "Adventures in Wood Finishing" he uses plaster of paris - ironic, since he lived in Paris at the time. He says
"The only filler I know that will fill pores fully is plaster of paris. Plaster of paris is available in several grades, the finest being the molding grade used by dentists and sculptors. This grade is the one that I used. The fast drying time of plaster of paris can be retarded somewhat by the addition of lime, and its hardness can be tempered with simple whiting powder. The composition of my filler was seventy five percent plaster, twenty percent whiting and five percent lime. To this mixture I then added dry colors."
Whiting powder is fine grade calcium carbonate and lime is calcium oxide or calcium hydroxide.
I recommend this book highly, even for experienced finishers. Very old school:
I do have 50 LBS of the molding grade as I used to do some victorein plaster work. I never ever thought of it for that use.You learn something new every day Bill.
A word of caution. Some of the plaster used in dental mold reproduction is very hard and can have a yellow cast. It's not your Cub Scout molding plaster. The "grinding" wheel used to trim the models looks like a circular rasp with teeth 1/4 in. long.
From a quick search it looks like different brands of dental plaster vary by color and hardness. If too hard, then there's the whiting powder.
I remember a story where he had some oak funiture in a bank or some place opening the next day and it was too light. as I recall he tented it and put a pan of amonia in the tent, by morning the color was dark,aged, oak
No experience with drywall but I have used egg whites, which is a very old-school method. I bet you have eggs in Trinidad.
Here is a link to a tutorial.
Egg whites have probably been in use since the Pharaohs, along with rabbit skin glue. All of these materials, BTW, are alternatives to primer and gesso for preparing artists' canvas. I've also heard of using a mixture of boiled linseed oil and either pumice or rottenstone.
I use drywall compound. Needs to be tinted a little darker than the surface when wet and thinned to a soupy consistency with water. I use water based acrylics from the nearest store with a crafts section. Burnt Umber (dark brown for Rosewood) or Burnt Sienna (reddish brown for Mahogany) will look natural in the pores when finished. Do test this on scrap piece and don't freak out if the dried surface looks too light. It will darken with the seal and top coats.
How much does it shrink, Mark?
How is it long term? what is the oldest job you have out there wusing drywall compound