| Official Luthiers Forum! http://luthiersforum.com/forum/ |
|
| Varnish witness lines. http://luthiersforum.com/forum/viewtopic.php?f=10101&t=48691 |
Page 1 of 1 |
| Author: | truckjohn [ Wed Dec 14, 2016 10:17 am ] |
| Post subject: | Varnish witness lines. |
Hey all, I am in the process of sanding and buffing out a J-45 build that I varnished with Behlen's Rock Hard varnish. This is my 6th guitar with the stuff.... For some reason - I have lots of witness lines where I never had that before.... I don't think there's much I can do about it now besides maybe try to hand rub varnish on top of the polished finish.... And that's most likely a really bad idea.... I may try it out on an out of the way spot - but I am suspicious that I will be causing more problems than I will solve... Be that as it may.... What do you guys recommend I try out next time to avoid witness lines? Here's my current method. I brush this stuff... On a freshly sanded bare wood - 1 heavily thinned coat as a sealer/spit coat. The rest of the coats are only thinned enough to allow good flowing and leveling while brushing - so I don't leave all sorts of brush marks. Knock down any raised grain and very lightly scuff with 320 Brush a coat Scuff Brush a coat Scuff Repeat usually 8 or 10 coats till I feel I have enough build to sand out without issue Let it dry a couple months Then sand it all out... I usually level with 320 dry and then wet sand up to 2,000, then polish with auto polishing compound. Thanks |
|
| Author: | Glen H [ Wed Dec 14, 2016 10:39 am ] |
| Post subject: | Re: Varnish witness lines. |
The only thing that I see that might contribute is using 320 grit to level. It might be too aggressive and remove more of the final coat than desired. Then following with more grits up to 2000 just is removing too much. So, in short, I just think you're removing too much of the final coat, thus going down into prior coats and showing the layers/witness lines. I'd try leveling with an 800 grit and going from there. |
|
| Author: | kencierp [ Wed Dec 14, 2016 11:07 am ] |
| Post subject: | Re: Varnish witness lines. |
Witness lines in a multiple coat varnish finish are usually caused by sanding through the top coat when doing the scuff operation. So I agree with Glen. Unfortunately almost impossible to detect at the time it happens. |
|
| Author: | Rodger Knox [ Wed Dec 14, 2016 11:34 am ] |
| Post subject: | Re: Varnish witness lines. |
I'd say it's the wet sanding, that's always caused witness lines for me. If it's the old Rockhard formulation, thinning it with 10% acetone and wiping on a thin coat or two might work. Another alternative is to wipe on a couple of coats of TruOil, I've used that over the old Rockhard with success. |
|
| Author: | Pat Foster [ Wed Dec 14, 2016 11:39 am ] |
| Post subject: | Re: Varnish witness lines. |
Brushing Behlens RH, I'd sanded through top coats many times when I was using it before the formulation changed to a polyurethane a few years ago. Witness lines weren't a problem unless I let it dry too long between coats. Even then, with sufficient curing time before leveling the last coat, a few minutes on a power buffer took care of the lines, but they were sometimes a challenge before I got the Stewmac buffer. I'm using Epiphanes now, with the same schedule as I used with Behlens RH. Pat edit: And, like Roger said, acetone helps, as suggested by Alan Carruth. But acetone likes to dissolve foam brushes. This I know. |
|
| Author: | rlrhett [ Wed Dec 14, 2016 11:48 am ] |
| Post subject: | Re: Varnish witness lines. |
Sent from my iPhone using Tapatalk |
|
| Author: | truckjohn [ Wed Dec 14, 2016 9:16 pm ] |
| Post subject: | Re: Varnish witness lines. |
So maybe slosh in a little acetone on the next go round? And don't wait too long between coats. What do you use instead of the foam brushes? I really dislike cheap chip brushes.... And I have not done well cleaning out expensive brushes. Thanks |
|
| Author: | violinvic [ Fri Dec 16, 2016 6:05 pm ] |
| Post subject: | Re: Varnish witness lines. |
I build up 6 or 7 coats of brushed varnish. Let it dry for a couple weeks. Level wet sand with 3200 micromesh. Let it dry a couple days. Put on 2 more coats, wet sand with 3200 micromesh between them. Let sit and dry for a long time. Buff out starting with 3200 wet sanded micromesh and work all the way up to 12000 micromesh. |
|
| Page 1 of 1 | All times are UTC - 5 hours |
| Powered by phpBB® Forum Software © phpBB Group http://www.phpbb.com/ |
|