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| Some truly horrible spray results http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=52579 |
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| Author: | cablepuller1 [ Sat Oct 26, 2019 1:52 pm ] |
| Post subject: | Some truly horrible spray results |
So frustrated with this, I have had good results in the past with these rattlecans (nitrocellulose) but getting horrible blushing now and the bracing is showing through the front !!!!! Temperature is 15°C and humidity is around 60%, sprayed like this before and been fine. Any ideas? Thanks    Sent from my SM-G960F using Tapatalk |
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| Author: | SnowManSnow [ Sat Oct 26, 2019 2:39 pm ] |
| Post subject: | Re: Some truly horrible spray results |
Humidity. I’ve had that issue. In my case it disappeared on the next coat Sent from my iPhone using Tapatalk |
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| Author: | cablepuller1 [ Sat Oct 26, 2019 2:40 pm ] |
| Post subject: | Re: Some truly horrible spray results |
SnowManSnow wrote: Humidity. Did you sand the coat of first ?I’ve had that issue. In my case it disappeared on the next coat Sent from my iPhone using Tapatalk Sent from my SM-G960F using Tapatalk |
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| Author: | SnowManSnow [ Sat Oct 26, 2019 2:54 pm ] |
| Post subject: | Re: Some truly horrible spray results |
cablepuller1 wrote: SnowManSnow wrote: Humidity. Did you sand the coat of first ?I’ve had that issue. In my case it disappeared on the next coat Sent from my iPhone using Tapatalk Sent from my SM-G960F using Tapatalk I just kept on w my schedule. I’m sure someone will have more help than I can offer Sent from my iPhone using Tapatalk |
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| Author: | bluescreek [ Sat Oct 26, 2019 3:13 pm ] |
| Post subject: | Re: Some truly horrible spray results |
what brand? I don't use anything but Minwax anymore |
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| Author: | bluescreek [ Sat Oct 26, 2019 3:14 pm ] |
| Post subject: | Re: Some truly horrible spray results |
what was your prep sealer filler stain water based etc |
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| Author: | cablepuller1 [ Sat Oct 26, 2019 3:54 pm ] |
| Post subject: | Re: Some truly horrible spray results |
bluescreek wrote: what was your prep Water based stain, zpoxy fill, tried Nitrocellulose sanding sealer but it also blushed and I had to sand it off, then sprayed with nitrocellulose satinsealer filler stain water based etc Sent from my SM-G960F using Tapatalk |
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| Author: | cablepuller1 [ Sat Oct 26, 2019 3:56 pm ] |
| Post subject: | Re: Some truly horrible spray results |
bluescreek wrote: what brand? I don't use anything but Minwax anymore This stuff, highly recommended and used before with little to no problems  Sent from my SM-G960F using Tapatalk |
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| Author: | Chris Pile [ Sat Oct 26, 2019 4:53 pm ] |
| Post subject: | Re: Some truly horrible spray results |
Yes, humidity. I never sprayed when it was over 50%. With rattlecans, you can't add retarder or anything to compensate. |
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| Author: | Glen H [ Sat Oct 26, 2019 5:36 pm ] |
| Post subject: | Re: Some truly horrible spray results |
Rub it with a soft t shirt type cloth. A little warming can go a long way. In a humid environment you need to apply lighter coats. And relax, there are ways to deal with blush. I’ve never had to sand it off. |
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| Author: | cablepuller1 [ Sat Oct 26, 2019 5:37 pm ] |
| Post subject: | Re: Some truly horrible spray results |
Glen H wrote: Rub it with a soft t shirt type cloth. A little warming can go a long way. In a humid environment you need to apply lighter coats Cool, never tried thatSent from my SM-G960F using Tapatalk |
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| Author: | B. Howard [ Sun Oct 27, 2019 4:52 am ] |
| Post subject: | Re: Some truly horrible spray results |
Oh my.... So much going on here and unfortunately little to do about it since we are rattle cans... If we had a gun we could adjust things. But we don't so we are here. Your spray pattern needs to be tighter, more overlap. Your coats are also very uneven with the blushing at the thicker areas. Most of this could have been avoided with better technique as your environmentals look fine for lacquer. What to do now? well if you can find a spray can of retarder you can use that to re-wet and let the moisture out of the coating. That or sand it off and try again. |
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| Author: | bluescreek [ Sun Oct 27, 2019 6:20 am ] |
| Post subject: | Re: Some truly horrible spray results |
Humidity must be controlled . You may have a bad can , this stuff does spoil. I stopped using most of the rattle cans , but I did find Minwax works well. I use it for touch ups for and I have done an few posts ok kgf and showed my process. Unlike a sprayer you don't have a lot of adjustment so you have to work with the can. I lay the surface I want to spray flat so I can spray a nice coat. Blush usually comes out. I have used ever clear and noblush from big A auto. Wipe this off with thinner or acetone. You also want sealer between your filler |
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| Author: | cablepuller1 [ Sun Oct 27, 2019 6:27 am ] |
| Post subject: | Re: Some truly horrible spray results |
Thanks guys, will sand off I think. Can I use shellac as a sanding sealer under the nitrocellulose as had bad blushing with the nitro sealer as well Sent from my SM-G960F using Tapatalk |
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| Author: | bluescreek [ Sun Oct 27, 2019 6:30 am ] |
| Post subject: | Re: Some truly horrible spray results |
yes I use Zinser transparent clear |
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| Author: | guitarjtb [ Sun Oct 27, 2019 9:45 am ] |
| Post subject: | Re: Some truly horrible spray results |
Spray another light coat, while the humidity is low, and the blushing will disappear. |
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| Author: | B. Howard [ Mon Oct 28, 2019 7:19 am ] |
| Post subject: | Re: Some truly horrible spray results |
cablepuller1 wrote: then sprayed with nitrocellulose satin Ah... The possibility exists that this is not all just typical moisture induced blush. And based on temp and RH given by the OP there should not have really been much blush. The possibility exists that what you are seeing is actually refractory paste used to make the finish satin that was not thoroughly mixed into suspension before spraying. These agents are thick and known to bve tough to mix in properly especially at lower gloss numbers. Rattle cans are even harder to mix up and if that can sat in inventory for a year it may take 40 minutes or more of shaking it to mix it properly..... |
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| Author: | Barry Daniels [ Mon Oct 28, 2019 9:18 am ] |
| Post subject: | Re: Some truly horrible spray results |
I think the fact that the blushing mirrors the bracing patterns on the top and back indicates that this is moisture related blushing. Stearate in the lacquer would not do that, but would make more random patterns. |
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| Author: | Mike Franks [ Mon Oct 28, 2019 1:30 pm ] |
| Post subject: | Re: Some truly horrible spray results |
I have used Mohawk & Behlens Blush Eraser for many years with great results. Just the lightest spray mist over the lacquer will completely remove the blush. It works best when the lacquer is fresh but also works when the lacquer is dry. I buy it from Stew Mac. https://www.stewmac.com/Materials_and_S ... raser.html Mike Franks www.mjfranksguitars.com |
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| Author: | Glen H [ Mon Oct 28, 2019 7:58 pm ] |
| Post subject: | Re: Some truly horrible spray results |
Sometimes I just spray lacquer thinner on it. Light mist usually clears mine up. Normally another coat does the trick. |
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| Author: | B. Howard [ Tue Oct 29, 2019 7:35 am ] |
| Post subject: | Re: Some truly horrible spray results |
Barry Daniels wrote: I think the fact that the blushing mirrors the bracing patterns on the top and back indicates that this is moisture related blushing. Stearate in the lacquer would not do that, but would make more random patterns. So the thinner sections of wood had more moisture in them? I doubt that. What I suspect is that the instrument was sanded with a RO sander and the spots over the braces were scuffed through the sealer which allowed the lacquer to absorb in those areas and that may have affected the flattening paste and how it aligned in the coating as it dried. The stuff behaves much like a fine metallic in suspension and though you cannot see it it flows around just like a metallic does as it dries. That brace shadow is why I never sand an acoustic instrument with a RO sander.... guitars are designed to vibrate freely and trying to sand them while they vibrate at at 30-60hz..... You always sand thin over the braces because of this. |
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| Author: | doncaparker [ Tue Oct 29, 2019 8:18 am ] |
| Post subject: | Re: Some truly horrible spray results |
B. Howard wrote: That brace shadow is why I never sand an acoustic instrument with a RO sander.... guitars are designed to vibrate freely and trying to sand them while they vibrate at at 30-60hz..... You always sand thin over the braces because of this. That's intriguing! Do you think the mechanism of injury is that the braced spots on the top provide more resistance to deflection, while the unbraced spots vibrate away from the sander? I am not disagreeing with you (I have no basis for disagreeing). I'm just trying to get a sense of how the problem happens. |
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| Author: | Barry Daniels [ Tue Oct 29, 2019 8:52 am ] |
| Post subject: | Re: Some truly horrible spray results |
This theory seems like a stretch. I have never seen this thinning issue from an RO sander and I use mine on guitars all the time. Edit 1: The reflection of the braces is more likely due to the thermal mass of the bracing which slows down cooling and moisture condensation. Edit 2: I added that last edit before I read Clay's post. You can see this thermal mass effect in windows and other areas where condensation occurs. Edit 3: The overthinning of the top above braces can be minimized by using fresh sandpaper. |
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| Author: | Bryan Bear [ Tue Oct 29, 2019 9:02 am ] |
| Post subject: | Re: Some truly horrible spray results |
I have seen this effect from sanding. I was doing a WRC top and got epoxy on the top while I was doing the pore fill. I decided to try a wash coat of thinned epoxy on the top to even things out. That was another mistake since it came out blotchy. I decided to try to sand all of it off and risk over thinning the top. I didn't use a power sander just a rubber block and (in retrospect) too much pressure to try to speed up the process. It didn't' take long for me to notice that the top above the braces was sanded through and the open areas much less so. I suspect this has happened to me before but I never noticed because I usually don't sand once the finishing starts (french polish) but it really taught me a lesson. The guitar ended up looking strange in certain light/angles but sounds good. It was for me so not a huge deal. |
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| Author: | Clay S. [ Tue Oct 29, 2019 10:05 am ] |
| Post subject: | Re: Some truly horrible spray results |
When I have had that happen I assumed it was because there was a temperature difference between the air inside the box and the air outside the box ("spraying" also cools the air) causing some condensation. The thicker places where the braces are glued lessen the reaction to the dissimilar temperatures. I found immediately moving the guitar body to a warm environment and placing it under hot lights eliminated the blushing. Mohawk "no blush" (butyl cellosolve in a rattle can) would be a handy thing to have if you are doing rattle can finishes (Buying a small compressor and a cheap jamb gun would be a better option in the "short" long run). |
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