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| CA filling nitro http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=43679 |
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| Author: | Tai Fu [ Fri Jun 20, 2014 12:13 am ] |
| Post subject: | CA filling nitro |
has anyone found an interesting phenomenon when drop filling nitro with CA? Basically somehow the CA reacts to the nitro in a strange way and wherever the CA has touched the nitro it would permanently alter it, causing it to sink more than the nitro around it. It shows up in a big way even after you sanded and buffed everything out. Why does it do that? |
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| Author: | johnparchem [ Fri Jun 20, 2014 12:42 am ] |
| Post subject: | Re: CA filling nitro |
CA should work as drop fill. One thing that I did find is that since it seems harder than the lacquer it is really easy to sand a dip around the CA drop fill. I stopped using sandpaper and use a straight razor blade to level. I do blend in with sandpaper after the fill is leveled. I also just fill a little at a time building up the drop fill. You can leave some lacquer out for a day to let it thicken and drop fill with it. |
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| Author: | Tai Fu [ Fri Jun 20, 2014 12:51 am ] |
| Post subject: | Re: CA filling nitro |
I thought so as well but like I was pointing out, wherever the excess CA contacted the finish, and this is on both my own nitro finish and a Kamaka uke I repaired a while ago, the nitro reacted to the CA and would always sink more than the original nitro no matter how much sanding or buffing I do. Even worse is when I tried to spray over it, and the nitro would also sink more than the other part wherever the excess CA touched the finish, so therefore it will not level out invisibly at all, or at least not until I polish it up and notice this goop around where I drop filled, level but still visible. The only way to fix it was to sand it off completely. I think the CA has something in it that somehow reacts with the nitro... |
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| Author: | Arnt Rian [ Fri Jun 20, 2014 2:30 am ] |
| Post subject: | Re: CA filling nitro |
I don't know about the reaction thing, but for sure nitro shrinks and moves more than CA over time, so even if you manage to get it OK looking when new, it will probably show over time. I never drop fill nitro with CA any more, the thick nitro trick works so better. You have to let it sit for a good while before leveling too, otherwise the drop fill will shrink more than the surroundings, and show over time. Drop fills in lacquer are not easy to get perfect, but as a guitar is used and gets its dings and scratches , its usually not that much of a problem anyways. |
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| Author: | Clay S. [ Fri Jun 20, 2014 8:26 am ] |
| Post subject: | Re: CA filling nitro |
There are a number of different formulations of CA and some seem to do as you say - react with the nitro and create imperfections in the surrounding finish. I have noticed this myself with loctite super glue. Others don't have this annoying property. |
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| Author: | Tai Fu [ Fri Jun 20, 2014 8:48 am ] |
| Post subject: | Re: CA filling nitro |
I can tell you Stewmac's CA does this too. |
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| Author: | dzsmith [ Fri Jun 20, 2014 12:03 pm ] |
| Post subject: | Re: CA filling nitro |
I tried CA on lacquer. I had a dyed finish under the lacquer. The CA spots were darker than the surrounding finish. I use lacquer now to drop fill. |
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| Author: | Haans [ Fri Jun 20, 2014 4:41 pm ] |
| Post subject: | Re: CA filling nitro |
A cardinal rule in finishing as long as I've been doing it is "Don't mix finishes". I've always used nitro, nothing else when I use it. The only exception I have ever made to that rule is when I do mandolins. In trying to replicate the old Gibsons, I always used spirit varnish over oil varnish. Why, you might ask, since they are incompatable. The answer is that I wanted to replicate the old Gibsons, which are all finish checked and that pretty much happens when I put spirit varnish over oil. I have tried the Gear Up cyano stuff a couple of times with fair success on finished guitars. I have repaired a couple of dings for folks with old (cheap) guitars, and it seems to work although I wish it was a little softer. I usually end up taping around the spot and sanding with a leveling stick and 600 grit to start and when I get it level, I remove the tape and move to finer grits. It works nicely, but I would still rather drop fill with lacquer and tell the customer to come back with the guitar in 3 months...or 6. |
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| Author: | uvh sam [ Fri Jun 20, 2014 4:46 pm ] |
| Post subject: | Re: CA filling nitro |
Plus one for Haans, just use nitro to drop fill and it should be able to be invisible |
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| Author: | ChuckB [ Fri Jun 20, 2014 5:09 pm ] |
| Post subject: | Re: CA filling nitro |
I tried CA to touch up lacquer before, pretty much the same method as Haans, tape around after the CA dries and level sand or scrape to tape level. Then remove tape and carefully level sand the last thousandth. But the touch up is not completely invisible, so I only use lacquer on lacquer. Chuck |
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