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Spraying nitro in the desert
http://www.luthiersforum.com/forum/viewtopic.php?f=10122&t=53195		 Page 1 of 2
Author:  flemsmith [ Thu May 07, 2020 12:08 pm ]
Post subject:  Spraying nitro in the desert
Not really sure what the humidity level is; I have a few meters, one in the kitchen says 24%, but the ones in the room where I keep a humidifier and my guitars just reads Er when it gets below 20%, and that's what they are saying now. The one in the workshop is broken, methnks. It's showing under 10%, but it's an analog meter and I don't really remember if it was working before.

I'm spraying the same Cardinal lacquer I used on two previous guitars with no problems (out in the shop where I have no humidity control) using the same HF touchup sprayer I've been using, always take it apart and clean after each day's spray, and spray cleaning lacquer thru it after each coat. The pattern looks fine to me in test sprays, seems to cover well with the overlaps. But it's drying quite rough; enough so that I'm having to sand with 320 after each day's spray. Seems to look and feel ok after the sanding, but I've never had to do that before.

Could the low humidity level be causing a problem like that? I'm using the Cardinal thinner at about 20%, which is what I've done before. I was thinking I might spread a little water on the floor before the next spray just to see if it acts more like I remember. Next post might say that I slipped and broke my wrist or something; mebbe I won't do that.

Appreciate any suggestions.

Roy in Az
Author:  flemsmith [ Thu May 07, 2020 12:40 pm ]
Post subject:  Re: Spraying nitro in the desert
Googling makes it seem like I need to confine my spraying to the early morning hours when it's cooler. Temperatures lately are getting above 100, but morning's are somewhere between 70 and 80ish. I'll try that and report back. Will slow me down, but that really doesn't matter. roy
Author:  Chris Pile [ Thu May 07, 2020 1:32 pm ]
Post subject:  Re: Spraying nitro in the desert
Add a little retarder so it won't dry as fast.
Author:  Barry Daniels [ Thu May 07, 2020 2:55 pm ]
Post subject:  Re: Spraying nitro in the desert
Yep, retarder should do the trick. The lacquer is probably drying before it can amalgamate.
Author:  flemsmith [ Thu May 07, 2020 11:55 pm ]
Post subject:  Re: Spraying nitro in the desert
Retarder....never bought any. Does it need to be the same brand? Thanks for the inputs, I'll start looking for some.

roy
Author:  Chris Pile [ Fri May 08, 2020 8:13 am ]
Post subject:  Re: Spraying nitro in the desert
All I ever bought was DuPont because that's what my local automotive paint store carried.
Author:  Barry Daniels [ Fri May 08, 2020 9:53 am ]
Post subject:  Re: Spraying nitro in the desert
I don't believe Cardinal makes a retarder.
Author:  Chris Pile [ Fri May 08, 2020 10:07 am ]
Post subject:  Re: Spraying nitro in the desert
Probably doesn't matter, Roy - but I'd contact whoever makes your lacquer and get their recommendation.
Author:  flemsmith [ Sun May 10, 2020 2:56 pm ]
Post subject:  Re: Spraying nitro in the desert
As per my normal, I didn't call anybody, just ordered what they had at LMI, figuring if they sold Cardinal, whatever retarder they sell should work with it. Not here yet, and I decided to just wait for the retarder rather than hope things are better in the mornings. I'll post again after I get it and spend a day spraying. I do appreciate the inputs. Even if I don't always follow direction so good. roy
Author:  flemsmith [ Mon May 11, 2020 11:29 am ]
Post subject:  Re: Spraying nitro in the desert
Success! Much better texture an hour after the first spray with retarder. I did start earlier in the morning too, think I'll stop for the day before noon; shouldn't be much above 90(ish) by then. I bought LMI's McFadden retarder, it's labelled for gloss lacquer, didn't even know you needed to match the lacquer to the type of finish you're trying to get. I really know little or nothing about retarder, but using mebbe 5% or so, there's no roughness in the surface at all now. Thanks, I appreciate being able to ask beginner questions and get experienced answers. Now that I have it, I'll google a bit and see what else I can learn about retarders. When you're just starting out you make mistakes..it's nice to get help that lets you correct them. Makes you feel like that second guitar should come out much better than the first. roy
Author:  flemsmith [ Mon May 11, 2020 6:30 pm ]
Post subject:  Re: Spraying nitro in the desert
great, ran out of nitro. After the 10th coat, but the first 7 had the drying problem. So I ordered more, kinda toying with the idea of letting this dry for about a week and see how it does leveling before I spray any more. I figure if it's hard to get rid of all the shiny spots, then I obviously need more, but if it seems to level ok, mebbe I'm thru spraying....does that make sense? So far I'm not so certain about the finishing process; came out great once, middling the second time, this is the third. roy
Author:  Chris Pile [ Mon May 11, 2020 8:29 pm ]
Post subject:  Re: Spraying nitro in the desert
It took me awhile to get it, too. You know what they say about practice....
Author:  flemsmith [ Tue Aug 11, 2020 3:20 pm ]
Post subject:  Re: Spraying nitro in the desert
First kit,000 from John Hall, very good kit in my opinion. The body has been 'curing' for a couple-three months now, thanks to covid isolating. The neck had to be resanded and needs re-lacquering, but I thought I could at least level sand the body. So I started with 600, went to 800, then 1000, thinking that grit level would keep me from sanding thru the lacquer....I kept spraying notes, but must have thrown them away so not totally sure how many coats I put on, but I think it was on the order of 16 or so. I've never been comfortable with the finishing process, and I have sanded thru the lacquer before so thought I'd stop and ask a que or two. Good news at this point is I have no obvious shiny areas that indicate poor coverage with the spray gun, and I have not sanded thru to bare wood anywhere. But I don't really know what it should look like in order to go forward, or whether I might need to go back to an earlier grit. Right now, the back looks pretty good, the sides have obvious pores (mahog) where I didn't do the z-poxy as well as I needed to, expect I just need to live with that. The top looks ok, but in the sun, it still looks to me like I can see sparkles from tiny little lacquer dots all over. So my que really is, how do I tell if I'm ready to go to the real fine grits, or if not ready, how coarse a grit do I need to go back to and how do I really tell I've done enough wet sanding at that grit. ie, when I don't really know what I'm doing well enough to proceed confidently what tips, advice can anyone offer? Thanks in advance for any input. Roy
Author:  Glen H [ Tue Aug 11, 2020 8:55 pm ]
Post subject:  Re: Spraying nitro in the desert
Are you going to complete the finish by hand or use a buffer?
Author:  flemsmith [ Tue Aug 11, 2020 10:49 pm ]
Post subject:  Re: Spraying nitro in the desert
by hand. The only buffer I have spins way too fast, I used it for polishing aluminum in the past. Tried once on a guitar with new buffing wheels and burnt the surface immediately. dang thing scares me around a guitar. I have sandpaper grit and Stew Mac papers that go to 7000. What I lack is skilled experience. roy
Author:  Glen H [ Wed Aug 12, 2020 7:16 am ]
Post subject:  Re: Spraying nitro in the desert
The only process I’ve used by hand is the micro mesh one. But generally a guideline with any sandpaper -leveling process is the next grit needs to remove the scratches from the previous grit. I sand across the path of the previous and sand unit I see no prior direction. I’m not sure what you mean by sparkles.
Author:  flemsmith [ Wed Aug 12, 2020 10:14 am ]
Post subject:  Re: Spraying nitro in the desert
Yeah, that description is a bit lacking....the more I look at it, I can't see any scratches; I'll look some more with a magnifier. In the sun, I definitely see tiny sparkles all over; I'm thinking they are just bits of nitro either from before I was told to use retarder, and the lacquer was starting to dry before it got to the guitar, or mebbe my spray gun technique was not atomizing enough. I do have some micromesh, starting at 2500 grit. I'm thinking I'll go back to 600 (mebbe even 400?) in an area, see if it knocks the 'sparkles' off without going thru the lacquer, then if it does, proceed the way you describe. BTW, seems like I read on one of Freeman Keller's posts that he would spray three or four coats in a day, then level sand with 350 or 400, and do it again until he had enough coats. Never done the sanding after each days coats, think I would worry about sanding thru. But since I'm just learning, open to experimenting til I have a process I have some faith in. Do you finish with a buffer, or is there a random orbital sander polisher that does a good enough job you can recommend. Thx for your input. roy
Author:  CarlD [ Wed Aug 12, 2020 4:53 pm ]
Post subject:  Re: Spraying nitro in the desert
Roy,
I've got 5" micromesh pads that work on my orbital sander 1500 to 20000 grit. Not quite the shine as I've gotten with a HF 3" pneumatic buffer, but is a lot easier than doing it with the small micromesh pads by hand.
Author:  flemsmith [ Wed Aug 12, 2020 7:51 pm ]
Post subject:  Re: Spraying nitro in the desert
harbor freight buffer? Both it and the orbital sander handheld? What speed should a guitar buffer run? My buffer is 3600 rpm. Scared to use it on a guitar. I used it to polish aluminum motorcycle parts. I'd be ready to spring for an orbital sander if I knew more about them and how the buffing material is secured. Hook and loop? Do buffing pads fit it as well? BTW, I dropped back to 600 grit where I can actually see the scratch pattern. Not in a rush, just want to learn what I should be looking for to know I've done enough work at that grit. Thanks. roy
Author:  CarlD [ Wed Aug 12, 2020 9:36 pm ]
Post subject:  Re: Spraying nitro in the desert
Yep, both handheld. Bosch random orbit sander. The MM pads are hook and loop. I might have got them at woodcraft or 2sand.com. I use them dry, tried them wet but that was pretty messy.
I don't sand with the HF 3" buffer, I use foam pads w/cutting Maguiars, then cleaner, then polish (lmii has them) for the final shine with a fleece pad and all at the 3000+ speed. It takes a pretty big compressor. It doesn't compare at all with a stand mounted buffer with 10" buffers, but I've never gotten to the level that I needed one. I have foam pads (from HF) that I tried on the orbital sander for the polishing compounds but the orbital action doesn't have the speed to create a shine (slows with pressure). Look up a thread comment by Barry Daniels about using a mechanical driven orbital sander about that issue.
About an orbital sander.... I use them to sand the finish with with Abralon sanding discs that work great with a vacuum on the sander, 400 thru a 1000. I've rarely sanded thru.
I try for 9 to 12 layers of sprayed on nitro, 3 to 4 coats a day and hand level sanded with 400 before sanding each day.
Have fun and stay safe,
Carl
Author:  flemsmith [ Fri Aug 14, 2020 4:45 pm ]
Post subject:  Re: Spraying nitro in the desert
Image

Back looks good, front fair. But I must have loused up the Z-poxy pore fill on the sides. The above is about the worst spot, but not atypical. Trying to decide what I can do about it now....I've wet sanded up to 5000, and was getting this sanded lacquer in the side pores starting at 600, which is where I started the finish sanding. Should I drop back to 320 or 400 on the sides and see how far into the lacquer I have to go to get down to where spraying more lacquer will cover the pores? I'm willing to do that, but if there was a way to do something any simpler, I'm all ears. Thanks for any advice. It's my first guitar build, I guess I could live with it and just do a better job on the next one I'm just starting. But I'd really rather fix it. roy
Author:  Glen H [ Fri Aug 14, 2020 5:54 pm ]
Post subject:  Re: Spraying nitro in the desert
Yea pores not filled completely. Building up enough finish to fill pores, IMO, isn’t worth it. It takes a lot and those look fairly deep. I’d spray a couple more and finish buffing it out. It’s your first. Believe me, when you string it up and play it you’re going to feel so proud those pores won’t make a difference.
Author:  CarlD [ Fri Aug 14, 2020 8:02 pm ]
Post subject:  Re: Spraying nitro in the desert
I agree with Glenn on just proceeding. I had a couple of the first come out that way using Zpoxy. Hesh had a website years ago were I learned his technique with Zpoxy. I think what got me over the hill was mashing it into the pores with the plastic card. He gave us a tutorial on it here...viewtopic.php?f=10117&t=20320&hilit=epoxy+fill. I still use that process but with West Systems 205 / 107.
Tried Aquacoat but could never get it to work. Six coats and the pores still showed thru the nitro. idunno
Author:  flemsmith [ Sat Aug 15, 2020 2:50 pm ]
Post subject:  Re: Spraying nitro in the desert
Understood. If I could just do something as simple as getting the white lacquer debris out with I dunno a toothbrush and some water, and then fill it back in with something darker I'd be all happy. Don't suppose anyone makes a dark car polish...?
Author:  flemsmith [ Mon Aug 17, 2020 7:04 pm ]
Post subject:  Re: Spraying nitro in the desert
lipstick on a pig? I didn't realize that automotive polishes actually do come in black...So now the sides look fine, with no white pore showing. The unfilled pores are still there if you refect the light off just right, but at any other angle, they look as good as the back does. So I'm taking advice to leave it alone, finish it as is, and resolve to do better on the next one. Roy
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