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| Question on lacquer sanding. http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=8902 |
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| Author: | Dave Rector [ Wed Oct 18, 2006 1:18 am ] |
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I have noticed in my past finishing efforts that I am able to see sanding scratches much more clearly in darker wood like EIR than I can in the lighter woods like spruce. This is a concern to me since my current build is all lighter woods (flamed maple/adi). Do any of you have an tips or tricks for being able to see your sanding scratches better on the lighter woods? I am assuming that good lighting is the first thing to accomplish, I have a bunch of floor stand type halogen light for this. Let me know if there are any other tricks. |
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| Author: | MontuoroGuitars [ Thu Oct 19, 2006 12:12 am ] |
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The only thing you can really do is look at the work as if someone else is judging it. It might take an extra 15 minutes or so. But if you look hard you will begin to see all those scratches. Try not to sand with anything more aggressive then 100 grit paper to statrt with. And if you use a Porter cable speed block finish sander with 220 at the end it helps take care of things much quicker. The weight of that tool really helps. I am sure I am telling you stuff you already know. But it has worked for me and sanding scratches drive me crazy. There is a wood sculptor by my shop. I always stop by to see his work. The stuff he works on has more twists and turns then the autobahn. And not a scratch in sight. If he can do it so can we. |
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| Author: | Dave Rector [ Thu Oct 19, 2006 12:51 am ] |
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Thanks guys! Hesh, I wasn't aware that the naptha trick worked on lacquer. I use it all the time on bare wood though. I'll have to give it a try. Frankie, I never start with a grit as low as 100 on a lacquer finish. I usually start with around 600 or so for the leveling and go up from there. Thanks for the input! |
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| Author: | MontuoroGuitars [ Thu Oct 19, 2006 3:30 am ] |
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Oh I am sorry!!! I misunderstood. I thought we were talking about bare wood before finish. Maybe I should reply to these after I have had some coffee. Still with the spped bloc sander you can sand DRY with 400 to level real quick. Then 600 WET. If you have a Buffing Arbor you can go from 600 directly to the Brown Menzerna Stick, Then to Fine. The end result for me has been a flawless finish. It almost looks too good if there is such a thing. You just cant beat Machine Buffing. It is truly amazing how fast sanding scratches go away. In seconds. And it also gives the true factory look. Meaning the finish heats up to just the right temp. Exposing just the right amount of grain line. Looks just like a 30's era Martin Finish. |
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| Author: | npalen [ Thu Oct 19, 2006 5:17 am ] |
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Frankie Don't you have problems loading the paper sanding lacquer dry? Perhaps you're using a stearated paper? Do you find that the smaller orbit diameter of the SpeedBloc works better when wet sanding? I've heard of others going directly from 600 to buffing but, in my experience, you have to be very aggressive and "melt" the lacquer into submission. Also, there are areas on the instrument where you can't be too aggressive without disastrous results. I assume that you do these areas with finer grit paper first? When you say that "the finish heats up to just the right temp", are you inferring that the lacquer becomes hot enough to flow and eliminate any sanding scratches. (I may be stirring the forum pot a little with that last question) I'm still learnin'. Thanks Nelson |
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| Author: | MontuoroGuitars [ Thu Oct 19, 2006 6:03 am ] |
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Yes the paper loads up after a bit. But you load multiple papers on then just tear them away as you go. I wet sand by hand not by machine sander. If you let the Laq. dry long enough you dont have any issues burning through at all. I spray my first 3 coats Shellac. Thats my sealer. Then I spray 9 thin coats of un-thinned Laq. I let that dry for 7 to 10 days. It is important to never of course sit too long in one spot when buffing with the Brown Menzerna Stick. When I refer to the finish heating up. Basically a machine provides a final result that a hand rubbing cant. Because of the friction involved from the machine. The machines I use are only 1100RPM. They are designed to polish plastics. And that is ideal for guitars. It heats up the Laq. just enough to even it out. In every spot. I can actually buff the entire guitar on the machine. Because I spray my necks and bodies seperate. Then assemble when the buffing is complete. I have tried so many ways to do this over the years. And I would not steer you wrong. It works so well I cant even convey the joy!!! Sounds silly but true. The Laq. you use is a very important part of it as well. As well is PSI and environment. I would be more then happy to further discuss this with you. I of course dont claim to know more then the next guy. I was told that it doesn't have to work for the rest of the world. As long as it works for you. |
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| Author: | Dave Rector [ Thu Oct 19, 2006 6:08 am ] |
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Nelson beat me to the question on this one. I have tried using a ROS with 400 grit 3m Gold paper on it to do the initial leveling. Didn't have much luck with it cause the paper kept loading up. I used to sand to about 800 grit and then take it to the buffer but on the last one I went through 1200 with the wet paper and I think it made a world of difference in how my finish looked. |
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| Author: | Michael Dale Payne [ Thu Oct 19, 2006 6:12 am ] |
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Next time try Micromesh 1500-12000 wet and I would dare you to find a sanding scratch (with the pneumatic ROS or by hand) Oh and get one of their backup pads for your ROS if you use the ROS. This makes the curvatures no problem 
Do Not use an electric ROS when wet sanding Please!  |
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| Author: | Dave Rector [ Thu Oct 19, 2006 6:54 am ] |
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Michael, I have an air powered DA sander. Unfortunately, my little Porter Cable compressor won't keep up with it. I've been doing the wet sanding by hand. 
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| Author: | Michael Dale Payne [ Thu Oct 19, 2006 7:02 am ] |
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Have you turned down the rpm (flow to the vien motor) and it still won't keep up? My 5h 30 gallon keeps up pretty good. |
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| Author: | Dave Rector [ Thu Oct 19, 2006 7:15 am ] |
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I'll give it another try Michael. I was thinking that I had turned the speed down, but I may have been trying to sand dry as well. I really don't remember, it's been a couple of years ago. These days if I can remember what I had for lunch I consider it a good day. 
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| Author: | Dean [ Thu Oct 19, 2006 11:02 am ] |
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I just had a visit to my shop by the 3m rep. We were discussing sanding scratches in final finishes. He told me that with all their products, except micron products, that the grit designation is an average. So, for instance, 400 grit may have particles as course as 100 and as fine as 600. This is why you see scratches no matter how careful you are. He advises for our type of finishing we should only use micron products because there is no variance in the grit particals. 400 is 400. Dean |
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| Author: | npalen [ Thu Oct 19, 2006 2:08 pm ] |
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3M Micron Dean--Here is some info on the micron graded paper. Grit comparison chart This comparison chart lists the micron grade beside the CAMI and P grades. We've had some discussions in the past about P grade also being held to closer tolerance on grit size. Nelson |
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| Author: | MontuoroGuitars [ Fri Oct 20, 2006 12:02 am ] |
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I guess I dont either. It seems there might be something else wrong along the way. I know I have mentioned it before. But do you guys like the Menzerna products? It seems that no matter how big the scratch the Brown Menzerna at 1100RPM works amazing. Using 3M Wet/Dry papers have never really been an issue. I am intrigued..... |
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| Author: | Dave Rector [ Fri Oct 20, 2006 12:06 am ] |
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My question wasn't really directed at the sandpaper. I was just saying that I have trouble seeing all the scratches. Once I see them I can get them out pretty easily. I was just interested in whether there was a better way to light things while sanding that would make the scratches show up a little better. It's all good info though. Thanks! |
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| Author: | Barry Daniels [ Fri Oct 20, 2006 12:58 am ] |
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I have had much better finishes since switch to 3M dry sanding papers (1000 and 1500 grit) and abralon pads. |
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| Author: | npalen [ Fri Oct 20, 2006 1:42 am ] |
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Barry--Are you using conventional 3M wet/dry in the "dry mode"? What grits are you using in the abralon pads? Thanks Nelson |
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| Author: | Dave Rector [ Fri Oct 20, 2006 2:51 am ] |
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Thanks Barry, could you tell us a little more about the dry papers and the abralon? |
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| Author: | Dean [ Fri Oct 20, 2006 5:30 am ] |
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My friend makes surfboards, and to find sratches and flaws he mounts flourescent tube fixtures horizontal on the wall at the same height as the top of the board on his workbench. Turn off any overhead lights and any flaws just jump out at you. I'm making an adjustable stand with a 3' fixture to do the same. Dean |
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| Author: | Dave Rector [ Fri Oct 20, 2006 6:07 am ] |
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Thanks Dean! That's exactly the kind of information I was looking for! |
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| Author: | Barry Daniels [ Fri Oct 20, 2006 7:14 am ] |
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I have only recently switched to the dry power sanding method, so I am still learning, but it has several advantages. The main thing is it is really quick. Also, when you dry sand, you can see immediately where you are at. You don't have to dry the surface in order to see how much further to sand. I do all the sanding with a Chicago brand, 3" pneumatic random orbital sander. This small tool works well for the flat or semi-flat parts of a guitar. About the only places it won't fit are the waist and back of the neck. I start sanding the final coat with P1000 grit 3M Hookit II Finishing Film. It is a stearated sandpaper that really resists loading. Then I go to P1500 grit. After this I switch to a 3" dia. Abralon pads in P2000 and then P4000 grit. At this point, I can bring the gloss up with a very light buffing using Menzerna fine or very-fine compound. (I haven't had luck with the brown colored, medium Menzerna) I haven't really timed the process, but to give you an idea of the speed, I would guess that I could take a peghead completely through finish sanding to final buff in 5 minutes, or even less. In areas that the ROS sander can't handle, I use the same sandpaper and Abralon pads by hand. On archtops I use an interface pad that keeps the edges from gouging in. I may never go back to wet sanding. |
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| Author: | Dave Rector [ Fri Oct 20, 2006 8:44 am ] |
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Barry, I've tried the 3m finishing films before and still have several boxes of them. The reason I quit using them was they kept loading up on me. Do you think I just didn't wait long enough for the lacquer to cure. Or maybe the speed on the ROS was a little high? |
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