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I recently had a failure with Rock hard varnish. This is after several successes. I just can't figure out where the process went wrong.

The real mystery is that while the finish on the bodies will not polish out, the necks, that were finished out of the same batch of thinned finish, turned out perfectly. I prepared the finish in the usual manner,applied finish to the bodies and then to the necks.

Any Ideas? I'm totally stumped.

cecil

When you state that a finish failed, could you be more specific? What did the product do or not do? Pals, Vic.

Was there any difference at all in surface prep between the neck and body?
ie, epoxy or other pore fill on body but not on neck? Any difference in application
technique?

And as Vic said, exactly what is "failure". Surface still tacky, bubbles, ???

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Gene

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I/m taking a wild guess but did you use rock hard when it was over 60% humidity? I/ve been to w, plains. (vy humid) I would only use varnish, when the humidity was under 50% did you brush or spray?? it could be any number of minor culprits.

I/m taking a wild guess but did you use rock hard when it was over 60% humidity? I/ve been to w, plains. (vy humid) I would only use varnish, when the humidity was under 50% did you brush or spray?? it could be any number of minor culprits.

The finish on the bodies simply will not buff our to anything close to an acceptable gloss. They look like I sanded to about 2000 grit and quit. I actually went to a 4000 grit abralon pad with an ROS. The results are blotchy and dull. The necks are as good as it gets.

The application was with the same brush out of the same container of mixed finish and thinner. I applied finish to the two bodies first and then the necks. Re coated within the hour for each successive coat. It's a mystery to me.

cecil

What's the wood on the body? Oil-based varnishes sometimes won't harden on oily woods like rosewood.

The wood is osage orange on one and sapele on the other. I have used this finish on both before with good results.

Some one ask about humidity earlier. It was 45%.

cecil

Those woods shouldn't be any problem. Got me.

Cecil: One post asked about different pore fill...................????
Tom

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A person who has never made a mistake has never made anything!!!

Tom
The pore filler was Zpoxy. I've used it forever and not had a problem with this finish.


cecil

That's a strange problem. Maybe there was some contamination on the wood from stearates in the sandpaper? Did you use the same paper for everything?

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PMoMC

I've never re-coated on that short a schedule, and I wonder if, perhaps, that has something to do with it? Maybe the finish just has not had a chance to cure all the way through.

When I first started using Rockhard varnish, I was thinning it with paint store mineral spirits. I did have some issues with it hardening slowly, and not polishing out right. Eventually it refused to harden at all, and when I looked in the can there was a white precipitate in the bottom. Since then I've used only their proprietary reducer for thinning, and have had no more problems of that sort.

It's strange that it seems right on one surface and not right on another, but I've had it with Rockhard. Something has changed. I used to have consistently good results with it, but the past couple of batches I've gotten have had big time problems both with hardening and with "grittiness" of texture. I recently had to strip the finish off of an archtop that I had attempted to finish with Rockhard (redid it in french polish and all is well). For me, that was it. I've moved on to Pratt and Lambert #38, and at least for now that's working very well.

I don't know what they did to Rockhard, but for a finish that I relied on for a long time, it suddenly became a problem and I'll not be using it any more.

Dave

Al I used the proprietary reducer along withe the acetone and kerosene you recommend. It may have been that I re coated too soon. The process of applying the finish to two bodies delayed the application to the necks so that it was longer than an hour between coats.

I'm also wondering if some of the solvents may have had time to evaporate out by the time I got to the necks add the resulting in a thicker film.

Dave I'll check into Pratt and Lambert #38. I think I can get it locally through the Shirwin Williams store. If so it will save me a 100 mile trip to obtain more rockhard.

cecil

As far as I can tell, the 'Rockhard' I'm getting now works the same as what I have been using all along, if not a little better. I can dream that I'm getting better at using it, of course...

There's your problem! With Rockhard varnish, I've found that it's best to do one coat per day. Two coats a day is pushing it and can lead to the underlying coats not drying. Re coating after an hour??? No way that is going to work. It's not lacquer, and needs exposure to air to cure. By recoating too soon, you essentially seal in wet varnish. I found this out the hard way myself a long time ago.

I've never had a problem using mineral spirits to thin, but I accept that I could just be lucky. I've probably applied at least several gallons of the stuff in my life, so I'm not inexperienced. Frankly, I typically use it straight out of the can, except for the last coat, which is thinned slightly with turpentine to improve flow out. This extends the dry time but results in a very smooth final coat.

It hasn't been mentioned but I find the ambient temperature is very important with this varnish. Around 70 deg is best. If it's too cold, it takes forever to dry. If it's too hot, it doesn't flow out as smoothly and will need more leveling.