Official Luthiers Forum!

I thought I might just create a thread with some running thoughts as I
finish my acoustic with Behlen's Rockhard varnish. I mixed it per Al
Carruth's instructions and am applying it the same way.

25% mineral spirits
5% acetone
70% varnish

I didn't do the drop of kerosene because I don't know where to find it.

I'm applying two coats a day, 8 hours apart (ish). Leveling before the
first, scuffing before the second. Brushing it on with foam brushes, a new
brush each time.

It's definitely not easy to apply smoothly. I applied three coats before
trying to level, scuffing before the third. The finish had developed some
definite valley's, and I almost had to take it down to wood (and did in
some spots) to level. Starting with 400, giving up and going to 320, then
finally to 220. The 320 and 400 load up in a near instant. With a 1/4
sheet sander, each 1/4 sheet was gone after a minute.

I'd been applying top, back, sides at the same time. After struggling so
much to level, I decided to stick to one area at a time. It will take longer
this way, but hey, I'm not in production I'm no longer hanging it by
my rope because I just couldn't control my brush as evenly as I'd wanted.
After applying a coat to the top this way, it's going on much smoother.

James, I'm very interested in hearing about your adventure here, please do keep us updated on your progress.

Thanks,
Greg

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Gwaltney Guitars

James I sure hate to discourage you but foam brushes is about the worst choice you could have made to apply varnish. You really should be using a good Badger hair brush. It will gone on so much better and level much easier. I know they are expensive but if it is properly cared for it will last many years.

_________________
Beautiful and unusual tone woods at a reasonable price.
http://www.rctonewoods.com/RCT_Store
The Zootman
1109 Military Rd.
Kenmore, NY 14217
(716) 874-1498

Here is a link.

http://www.constantines.com/browseproducts/Badger-Hair-Brush .HTML

_________________
Beautiful and unusual tone woods at a reasonable price.
http://www.rctonewoods.com/RCT_Store
The Zootman
1109 Military Rd.
Kenmore, NY 14217
(716) 874-1498

James, I've done a lot of work with Rock Hard. (Still don't have the guts to do a guitar in it yet but will soon).
As Bob said, you NEED to put it on with something nice. Get yourself a 21/2 to 3" badger hair brush. Also when you sand you need to add water to the equation. Wet sanding is really the only way to make it work. And to do that you need good automotive papers. (or other finishing paper) It will not load like yours has done.

I have used foam brushes with good results. The trick is to apply and not go over and try to smooth it or fix what may not look good... Apply and let it dry... level sand after a few coats.

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

Thanks for the input guys. I'm definitely going to use water (I am using
automotive papers).

Thanks for the tip on the brush, too. $10.95 isn't anything compared to
a compressor and spray gun. I'm using the foamies because Al had said
it just makes for a lot less trouble when it comes to cleanup. If I
remember correctly, I read that he thought you'd have to spend a long
time after each coat cleaning the brush if you didn't want dried varnish to
flake off the bristles.

Paul, what do you clean this stuff with if I do decide to get a brush? This
might sound funny, but will it eat up my skin?

Clean up with mineral spirits (paint thinner). Also another tool worth investing in is a brush spinner. Dip your brush in some mineral spirits and stick the brush in a clean 5 gallon bucket with the brush attached to the spinner. Pump it a few time and the spinner "spins" the brush and centrifugal force slings the thinner and varnish out of the brush onto the walls of the bucket. A few dips and spins and the brush is clean and it takes far less thinner. You can follow up with washing the brush in hot water with a bar of Fells Naptha soap and allow the bristles to dry. This will keep the brush nice and soft and will not have any flakes in it or stiff bristles.

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tim...
http://www.mcknightguitars.com

I have finished seven guitars with rockhard varnish and have switched to foam brushes after using all kinds of expensive bristle brushes. The problem with regular brushes is that if any, and I mean the least bit of varnish dries in the brush or in the ferrule you get these tiny particles of sand (dried varnish) that show up the next time you use the brush. If any varnish gets into the ferrule while you are using the brush or cleaning it you have to throw it away.
You have to start with very good preperation-sand the guitar to at least 320 or 400. I have a handle I made that uses the neck bolts so I have a way to hold the guitar while I brush on the finish. I clamp the handle in a vise with the guitar horizontal and brush the back, then do the sides holding the handle and then clamp in the vise again and do the back. It helps to look at the guitar at a low angle in good light to check for missed spots and don't over brush - get a surface covered quickly with long strokes. If you have to go back over something after a couple of minutes it just makes things worse.
I scuff sand after every coat with a norton sanding sponge (about 400) and level sand before the last coat (usually the sixth or seventh) with 3M gold (400 to 600) which does not load up badly at all.
Then I wait, and the longer the better. It is possible to buff out after a week, but the last guitar I did was a spec guitar and it sat for over a month before I had time to get to it and it was much easier to sand and buff out than any of the ones I had done before. I start with 600and 800 gold paper and then go through Micro mesh to about 3500 or 4000 and then go to the buffer.
I find the foam brushes will level the finsih very well if the mix is right. I use turpentine instead of mineral spirits and a few drops of kerosene and it self levels very well as it dries.
Varnish is a pain, I can't deny it, but I love the look. It doesn't have the plastic look of some finshes and it turns spruce a really nice color - it look fifty years old as soon as you finish.

                            Peace, Paul

James, if I know I'm going to be doing a lot of subsequent coats, I'll fill a container with the Rock Hard reducer and just soak the brush in that. Only cleaning it good after the last coat.
When cleaning a brush I use a wire brush and sort of "push" the paint out of it from the ferrel to the tips of the bristles. I don't have a spinner so that is probably the next best option.
Oh on the sanding thing: If you put a dab of Murphy's oil soap in with your water, it works even better. I have a spray bottle that is 10:1 water to oil soap and just spray it on the surface as I'm sanding.

James,
I tried all kinds of brushes. What worked best for me was paper towels. Get the ones without any embossing, just plain and smooth.
BTW - I never got it to work to the point that I was happy with it, so I ended up spraying it. I love the finish.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

Hey everyone

I just came in from taking the soundboard back to wood, sanding to 320,
and applying a coat with a brush. MUCH better flow. I'm using a 2" poly/
natural blend brush. Couldn't find badger anywhere in town, but felt all
the brushes at a good shop and chose the softest. Thank you for the
brushing suggestions.

Steve, wiping it on seems really interesting. Do you thin it somehow?

James...you might want to get in touch with Bruce Sexauer(over on the 13th Fret). He does the Rockhard varnish on all his instruments and has a lot of experience with the stuff.

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Hank Mauel

Thanks for the heads up, Hank. I'm happy with what was happening with
the new brush, so we'll see where it goes.

But{/I] . . . yesterday I decided I couldn't live with some fit issues going
on with the back and removed it

It should be glued back on by tomorrow evening though, and I'll start the
process all over again.

I had to order some new spiral bits for the binding channels, so I decided
to order the badger hair brush as well.

James,
You can thin it or not. I think it is best to thin it, at least up until the last coat. The last coat needs to be thick enough to allow you to level sand and polish without breaking through. I had better luck wiping than brushing. All I read on brushing said that people were looking for the ultimate brush. Perhaps it does not exist. Paper towels are cheap with no cleaning.

The other problem I had with it was dust. It was a dust magnet, and because it takes so long to dry, it could collect dust longer than I could keep the area dust free. I now use Crystalac, which dries very fast, is hard and looks great. My best advice to you is to use it instead of the RockHard.   Crystalac will also burn into previous coats, Rockhard won't.

_________________
"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

I don't use foam brushes myself: the whole point of the thinned varnish is that you can pull it out a lot, so that when the acetone flashes off it won't run. I don't know how well it would work without the kerosene though: that's a brushing agent that keeps the brush from sticking as you pull it. As is often the case in guitar making, this is a system, and it works best if you don't leave things out or make major changes.

These days I'm using a reasonably soft 1-1/2" bristle brush. I used to use a much wider one, but this works really well.

If you're careful to only dip about 1/3 of the length of the bristles into the varnish you should not get any up into the ferrule. This will really cut down on the 'sand'.

After cleaning the brush out with thinner/reducer, I wash it with soap and water every time. I learned this from a student who is a commercial artist, and has brushes that cost $200 each. There is no way you can get out all of the varnish, but you can come darn close, and preserve the brush for a long time by careful washing. I probably spend longer washing the brush than actually varnishing. The neat thing is that the more you wash it, the softer and better the brush gets.

I don't usually go past #220 sandpaper in the prep, but I do make sure I've got a really level surface. I learned what 'level' is when I started Fench polishing. Now I do the same sort of prep for anything.

With a good level surface, and following this system, I don't get enough 'sand' or dust in the surface to require much sanding at the end. Once in a while I'll we sand something after I've put on three or four coats, but generally don't need to do that either these days. I scuff back with #1800 or 2400 Micromesh between coats, and canoften get away with just #2400 or 3200 in the end, followed by Novus polish. The longer you can let it set up at the end, the better.

James, here is a past discussion of Behlen application.
link

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Don Atwood
Arlington, VA

Great notes guys!

The badger hair brush should be here in a few days. I expect to be back
at it some time next week once I get the back back on and rebound.

I've been pulling it out pretty thin, to the point that it trails to nothing.
How thinnly do you pull it out?

Where do you go for kerosene? The local hardware store only sold it by
the gallon for $12.

Sometimes you can get kerosene as lamp fuel in quarts. When we bought our old house near Boston thirty years ago there was half a barrel in the back yard, left over from the greenhouse heater my wife's grandfather used. I'm still working on that stuff. Around here so many people use it that many of the gas stations sell it. I bet if you talked with the folks there, they'd give you a dribble: a cup would be a lifetime supply for this application.

I would never sand bare wood any finer than 220 grit unless I was doing an oil finish.   Finer than that leads to finish delamination with film finishes.   This was proved out both in my shop and at SCGC.