| Official Luthiers Forum! https://luthiersforum.com/forum/ |
|
| Wet sanding & polishing https://luthiersforum.com/forum/viewtopic.php?f=10101&t=54168 |
Page 1 of 2 |
| Author: | flemsmith [ Mon May 24, 2021 1:30 pm ] |
| Post subject: | Wet sanding & polishing |
2nd guitar,16 coats Cardinal gloss lacquer, cured 30 days. Started wet sanding with 600, 800, 1000 and 1500. Can already tell this is gonna look much better than my first which only looks good inside from mebbe 5 feet, but I need to ask a couple que's...I don't have major shiny spots, so feel good about my level sanding before the lacquer spray. But I do have tiny shiny dots in a number of areas. Trying to decide whether to go back to 6 or 800 and get rid of all of them (hand sanding), or try the new random orbital with some medium (or coarse?!) compound and see if that gets rid of them. Truthfully, you can't see them unless you go out in the sunlight, and I'm always worried about sanding thru the lacquer. As long as I'm asking, when wet sanding, should I use separate water jugs for each grit? I have seen a few scratch lines the paper generated from my wet sanding technique. Learning is fun when I'm not screwing up; (ie, getting more experience). Thanks, Roy |
|
| Author: | Clay S. [ Mon May 24, 2021 1:55 pm ] |
| Post subject: | Re: Wet sanding & polishing |
You could try compound on a cloth and buffing those spots by hand to see if buffing will remove them. When changing grits I change the water as well. Loose grit will wash off the sandpaper and can be picked up by the next finer sandpaper if the water is not changed. I like to use a small amount of dish detergent in the water for wet sanding, and then rinse off with clean water. |
|
| Author: | jfmckenna [ Mon May 24, 2021 2:07 pm ] |
| Post subject: | Re: Wet sanding & polishing |
If you have to hold it up to the light to see it, IOW you have to look real hard to see it, I would just move on. There's nothing worse then sanding through a finish! Then again there are people like this out there too  https://www.acousticguitarforum.com/for ... p?t=616343 |
|
| Author: | bluescreek [ Tue May 25, 2021 9:34 am ] |
| Post subject: | Re: Wet sanding & polishing |
if you mean shallow sink areas you need to level sand a bit more. Do you know how thick the finish is? That small amount will help the final buff out a lot |
|
| Author: | TerrenceMitchell [ Tue May 25, 2021 3:04 pm ] |
| Post subject: | Re: Wet sanding & polishing |
Just out of curiosity... this is a solid body instrument, yea? |
|
| Author: | phavriluk [ Tue May 25, 2021 4:46 pm ] |
| Post subject: | Re: Wet sanding & polishing |
I can only comment on my own experience. Shiny spots are areas where when sanding, the surrounding area is higher than the shiny spot. My technique is to spray a cross coat/let dry/sand/inspect/repeat till no more shiny spots/areas. Took a while, but when I didn't find any more shiny spots I was done with applying nitro. I know car painters apply a bunch of finish and and sand till satisfied but I was finishing guitar not a Chevy. |
|
| Author: | bluescreek [ Tue May 25, 2021 6:26 pm ] |
| Post subject: | Re: Wet sanding & polishing |
the most common mistake in finishing is too much finish and not knowing how far to go in level sanding. I suggest that when spraying finish , lay a few pieces of tape at the fret board extension area . After every 3 or 4 coats peel and measure , it may not be the most accurate but will get you an educated guess. I used to shoot about .016 on now I stop after .012 |
|
| Author: | flemsmith [ Wed May 26, 2021 8:34 am ] |
| Post subject: | Re: Wet sanding & polishing |
This is a 14 fret 000, granidilla and cedar. Next time I will definitely mask off the area under the neck. Sounds like a good way to try and check the lacquer thickness, assuming my calipers and I can measure it repeatedly. I really don't see areas that are shiny like it needs more levelling. What I see are tiny dots that did not all go completely away when wet sanded at 800, not visible til I take it out in the sun. I don't think there is a big downside to go ahead and polish from where I am now. This is such an improvement from my first build I have to see how good it might look with some polishing. On number 3, I will mask off the bridge and neck overhang areas and measure the thickness. Having a number (.012") in mind sounds like a nice process improvement. Thanks, Roy |
|
| Author: | phavriluk [ Wed May 26, 2021 8:46 am ] |
| Post subject: | Re: Wet sanding & polishing |
An opportunity available to builders working on their own guitars is that they can ignore the compromises in techniques that commercial builders must pursue in order to stay solvent. And I think doing things well as opposed to doing things fast is a luxury that we as builders for ourselves ought to be aware of and exploit. No reason to copy factory practices, factories attend their own dance. |
|
| Author: | Barry Daniels [ Wed May 26, 2021 4:35 pm ] |
| Post subject: | Re: Wet sanding & polishing |
Sounds like you might want to revisit your pore filling procedure. That is probably the cause of the shiny dots. |
|
| Author: | James Orr [ Thu May 27, 2021 7:54 am ] |
| Post subject: | Re: Wet sanding & polishing |
Can you post a picture? Sent from my iPhone using Tapatalk |
|
| Author: | flemsmith [ Fri May 28, 2021 9:29 am ] |
| Post subject: | Re: Wet sanding & polishing |
Pore filling...you are right, there are a few places where even after three coats of Z-poxy I can see some wood pores that did not get filled completely, mostly on the sides close to the waist. I never mentioned it because I am confident I can learn to correct it. But that's not really related to the 'dots' I see, which are much smaller; I'm beginning to think they may be related to the low humidity when I sprayed. Don't suppose a better quality spray gun would help? Can I take a picture that captures it? I kinda doubt it, but I'll give it a try and see what happens. After polishing, I'm pretty darn happy with the results as a pretty big incremental improvement, a nice positive reinforcer for continuing to aim for better results on the next. |
|
| Author: | flemsmith [ Sat May 29, 2021 11:44 am ] |
| Post subject: | Re: Wet sanding & polishing |
OK, here's a coupla pix. Hard to take in reflecting sunlight, and does not really show all the tiny dots. Does, however, make it look like I could do some more sanding/polishing before I call it good....!?   Guess I could go ahead and strip off the lacquer under the neck before I decide, that should let me measure the lacq thickness. I'd rather leave it as is than sand/polish thru the lacquer. I am curious how much pressure one uses with the Random Orbital polisher, I did not add much to it's own weight. Roy |
|
| Author: | phavriluk [ Sat May 29, 2021 1:35 pm ] |
| Post subject: | Re: Wet sanding & polishing |
Laying down finish ain't near as important as cutting it back (with a block) to as level as possible without striking wood, and repeating till there ain't no more shiny spots. |
|
| Author: | James Orr [ Sun May 30, 2021 11:01 pm ] |
| Post subject: | Re: Wet sanding & polishing |
Those are spots that didn’t quite get level. I’m super glad you’re happy with the improvements you’ve made! Next time you see something like that pop up, it just means that you need to level in that area a bit more. Leveling is the worst. I do the bulk of mine with 600 grit in my Festool ETS-125. It’s really nice to have small hard blocks with rounded edges to touch up small areas like that. It’s definitely possible to get small pits in areas that didn’t get filled enough, but those literally look like little pits. Glu-Boost Fill-N-Finish is perfect for that kind of situation. This is different than that though. This is just an area that didn’t quite get level. Sent from my iPhone using Tapatalk |
|
| Author: | flemsmith [ Tue Jun 01, 2021 11:32 am ] |
| Post subject: | Re: Wet sanding & polishing |
After a few days of doing other stuff while I let the leveling/finish on this one stew in the back of my head, I decided to go after it again starting with 600. After all, this is the build I'm trying to learn improvements from, worst case I sand thru the lacquer and have to respray. Plus, it should help me understand stuff like, how hard do I 'sand' at this stage. I ended up going after the top at least 8 or 10 times with 600, the last 6 or so using new paper. I do have some dishwashing drops in the water. I'd clean it off and go out in the sun after every step in the process. And I am using the 45 degree method, where I'll change direction when I go to the next grit. Good news is that nearly all the shiny spots are gone, I could see them gradually disappearing after the first few processes. I'm debating whether to go to 800 now or keep after it til every single spot is gone. I was using a fair amount of pressure, and one of those 6" erasers as my backing block. Not sure if I can finish it today or not,(other stuff needs doing), but I am sure I can get it even better than before I asked for help. Thanks for the inputs, they definitely helped. Not just anywhere an absolute beginner can get expert advice just for asking. It is really appreciated. Roy |
|
| Author: | Ken Lewis [ Tue Jun 01, 2021 11:47 am ] |
| Post subject: | Re: Wet sanding & polishing |
Yes, I would move on to 800. I usually only spend a short amount of time with the 600...just enough to remove the bulk of the high spots. Most, if not all of the shiny dimples I work with 800. 800 grit still has a fair amount of cutting but once you move on to 1000 I find I've moved more into the polishing stage than surface removal. Seems like you're on the right track. Be mindfull of working the edges. Sand up to but try not to dip down. Best of luck. |
|
| Author: | flemsmith [ Tue Jun 01, 2021 5:18 pm ] |
| Post subject: | Re: Wet sanding & polishing |
Went back to 600 and started again. Got rid of all the little dots, but ending up with a slight edge sandthu.  Looks much better, but it's not really 'glossy'. And in the sun I can see very slight remnants of some of the wet sanding. |
|
| Author: | phavriluk [ Tue Jun 01, 2021 9:58 pm ] |
| Post subject: | Re: Wet sanding & polishing |
Looks like another application of finish and blocksanding the result. By leveling each application there is little chance for buildup. It's a treat to see this even and smooth finish emerge from the repetition. |
|
| Author: | Pmaj7 [ Wed Jun 02, 2021 12:56 am ] |
| Post subject: | Re: Wet sanding & polishing |
Are you using 600 or p600? The 600 is more than 50% finer than p600. Pat |
|
| Author: | James Orr [ Wed Jun 02, 2021 1:14 am ] |
| Post subject: | Re: Wet sanding & polishing |
flemsmith wrote: Looks much better, but it's not really 'glossy'. And in the sun I can see very slight remnants of some of the wet sanding. Great work. The work involved in finish is frustrating, but you’re doing great and learning valuable lessons. It won’t get glossy until you hit it with some buffing compound. What you see now—a satiny finish with sanding swirls—is exactly what it should look like right now. Once you touch up that sand through and level at 600, hit it with 800, then 1000, 1500. You’re likely ready to buff at that point depending on your chosen method. My first guitar was buffed by hand with 3M compounds and an old T-Shirt. Continuing to 2000 would be best if taking that route. Sent from my iPhone using Tapatalk |
|
| Author: | Clay S. [ Wed Jun 02, 2021 7:50 am ] |
| Post subject: | Re: Wet sanding & polishing |
Hi Roy, Not knowing your familiarity with using a spray gun I will offer these tips: When spraying an item that I am going to level sand and buff, I will first "band-in" the perimeter with a coat of finish and then cover the entire surface with a coat of finish. This has the effect of double coating the edges so there is more "build" on the areas you are more likely to sand through. When level sanding with a powered sander I will stay away from the edges of the piece and later sand them smooth by hand with a block sander. When buffing you should also avoid allowing the buffing wheel to wrap around the edge of the work, as this will also burn through the finish in very little time. Areas of "sand through" rarely have as many coats reapplied to them as the original finish, so you must be careful not to remove too much finish when sanding and leveling these areas. |
|
| Author: | flemsmith [ Wed Jun 02, 2021 9:16 am ] |
| Post subject: | Re: Wet sanding & polishing |
Thanks all. I actually did buff before the last picture, not that I know any more about how much pressure to use buffing than I do sanding. I'm using Maguir's Ultra Cut, Medium, and Stew Mac Fine. I'm not very experienced with a spray gun, (this is the 4th guitar I've sprayed) and I'm using one of the little harbor freight guns, I do try to keep it cleaned after each day's spraying, and I spray some lacquer thinner thru it after each spray session. The edge that's showing is quite small, should I really spray that again, or can I use a small brush to fill that area? I've gotta do some other stuff for awhile, will get back to this when I can. Roy |
|
| Author: | phavriluk [ Wed Jun 02, 2021 11:50 am ] |
| Post subject: | Re: Wet sanding & polishing |
My uninformed opinions? No brush. Respray, emphasis on the edges as described above. If there was bare wood exposed, there's more where that came from. Lots of talk about final buffing, I prefer to see a good, filled, level surface first and worry about buffing later. |
|
| Author: | flemsmith [ Fri Jun 04, 2021 10:22 pm ] |
| Post subject: | Re: Wet sanding & polishing |
Respray how many coats? Just like I was spraying to begin with? Mebbe three in a day, then level again in the morning (starting with 600? or mebbe 400?), then do I let it cure a few weeks again before wet sanding? Y'all may not realize how little I really know unless I've actually done it before. I'm travelling a bit, so will be awhile before any more results. |
|
| Page 1 of 2 | All times are UTC - 5 hours |
| Powered by phpBB® Forum Software © phpBB Group http://www.phpbb.com/ |
|