Official Luthiers Forum!

Hello all,
I ran my tests (practiced) on my scraps with brushing Rockhard using the recipe found here....dilute 20% with their thinner, 5% acetone, and few drops of kerosene. This is working very well and looks great. I am using a foam brush which is suprisingly easy and does not leave any brush marks.....as long as you have a smooth stroke and do not stop and go when brushing.

I am having only one issue however and wanted to ask the advice of the forum. When I brush on the varnish I am only using the weight of the brush. I do not put any downward pressure....thus leting it flow out of the brush instead of squeezing it out. At the end of the stroke when it reaches the edge of the wood I try and lift it up to have the flow out stop directly at the edge. This is hard to do and most of the time I brush off the edge making sure the brush does not hit what is under the piece and contaminating it. At the end of each strok there is a ridge of slightly thicker/higher finish. I tried to combat this by overlapping my strokes by 50% and it does help but the ridge is very visiable still....even looking directly at it and with no strong back light. I tried a coat or two with an even more diluted mix to see if I can get the finish to level out even more...it helps but not enough. I thought this ridge would level out when left alone but the sanding and leveling shows that it is still there. I wonder if it is because my edge is not rounded that much on my test piece and when I do the real thing this will not happen due to the slightly rounded edge of the guitar? I also tried a natrual brush to see if it was the brush and got the same results.

Have you guys run into this? The finish is level everywhere except the ridge on the edge. Will the final rub out take care of this....I do not want to burn through all over the edges.

Thanks for any advice!

Matthew

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I use an inexpensive bristle brush that I got at the hardware store, and it works pretty well. Clean it out with soap and water after a few dips and sqeezouts in paint thinner. If you keep it up well it will just get better with age, sort of like an old luthier.

It's unclear to me whether you're simply 'laying on' the varnish or actually brushing it out. Thin spirit varnishes have to be laid on: you apply a brush full with a single stroke along the grain (say), and put the next stroke down adjascent to it but without the new stroke ever actually touching the last one. The following coat goes on the laps. If you try to brush the stuff out it looks like a plowed field.

With oil varnish you need to brush it out. Dip the brush in to about half the length of the bristles, or a bit less. Lay on two or three dabs along the grain, say in the upper bout of the back. Spread those out across the grain, being careful to avoid brushing onto an edge. Then finish off by brushing out along the grain again with fairly slow side-by-side strokes and light pressure. With a 1-1/2" or 2" brush you should get the whole upper bout with one brush full. The lower bout takes about two. Always work from a wet edge. If you're quick enough you can actually brush out the entire back along the grain when you get the last brush load applied. The coating should be thin enough and have bodied up enough by this time that it won't flow toward the edges.

My apologies if this is what you're already doing. As I say, it was unclear to me in your post: I'm easily confused.....

Thanks for the advice. I will see what I can come up with.

You definately need a very good brush with the oil varnishes, and Alan has detailed out how I
learned to varnish old mahogany speedboats (Chris-Crafts, Century's, etc). The first brushing
across the grain gets the varnish covering the surface, the final light "tipping-off" levels out
any uneven areas (called tipping-off, I believe because you just use the very tip of the brush.
Often the weight of the brush alone is enough pressure). Work on achieving few to no bubbles
on the surface of the varnish both during the initial application, and the final tipping-off.

_________________
Gene

Politicians and diapers must be changed often, and for the same reason- Mark Twain

Couple more things. The ridge at the end of the stroke is from stopping, slowing or lifting. carry the stroke off of the edge. this means you will need to wipe off the drip in the descending surface. Don't even allow the full weight of the brush to ride on the surface. Keep your hand forward of the stroke, pull the brush with the and. the varnish is to flow out the back side of the brush, brush barley on the surface, 1/4 width overlap is plenty. 1/2 width overlap and you are really piling on the varnish. and run the risk of pulling over pre gelled varnish. And of course never back stroke or go back over within a session.

I too suggest a top end badger bristle or china bristle brush for smoothest flowout