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| Nitro Cure Time - Dry Box http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=37026 |
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| Author: | NWflyonly [ Fri Jul 06, 2012 6:11 pm ] |
| Post subject: | Nitro Cure Time - Dry Box |
There have been threads on dry boxes that help expedite the curing process of various lacquers but I don't recall the overall cure times. Is there a way to determine if/when the lacquer is cured. I live in a "Dry Box" the desert of Arizona and my garage is quite warm throughout the day which is where I let my lacquered guitars cook I mean cure. I just don't know how to tell if they are done? I've tried sticking a toothpick in the center (as per my wife's recommendation") but I don't think it's telling me much...other than not to listen to my wife...which for the most part I'm pretty good at doing most of the time. Thanks in advance for any input or advice. |
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| Author: | bluescreek [ Fri Jul 06, 2012 8:01 pm ] |
| Post subject: | Re: Nitro Cure Time - Dry Box |
The dry boxes that I saw that worked had a complex filter and air control system. |
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| Author: | John Arnold [ Fri Jul 06, 2012 8:08 pm ] |
| Post subject: | Re: Nitro Cure Time - Dry Box |
In my experience, you don't need heat, just air circulation. I have seen lacquer dry just as fast at 20 degrees F. as it does at 80....provided the humidity and circulation are similar. After spraying lacquer, I use a fan on it for a few days. Shop windows are open. I test lacquer hardness by pressing it with a thumb. If it leaves a print, it is not cured. Also, if it smells like thinner, it is still outgassing. |
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| Author: | Carey [ Fri Jul 06, 2012 11:01 pm ] |
| Post subject: | Re: Nitro Cure Time - Dry Box |
I agree with John Arnold's advice. A couple of other things: if possible, start your cure slow, eg not too warm or dry, and ratchet it up after a few days. The finish tends to case harden otherwise. Also, are you giving the last coat a light scuff w/ 320 or 400? This too will help with an even cure. |
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| Author: | Nils [ Fri Jul 06, 2012 11:17 pm ] |
| Post subject: | Re: Nitro Cure Time - Dry Box |
Just go by smell. Once it doesn't smell like thinner you're set. |
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| Author: | TonyFrancis [ Sat Jul 07, 2012 12:16 am ] |
| Post subject: | Re: Nitro Cure Time - Dry Box |
Carey wrote: I agree with John Arnold's advice. A couple of other things: if possible, start your cure slow, eg not too warm or dry, and ratchet it up after a few days. The finish tends to case harden otherwise. Also, are you giving the last coat a light scuff w/ 320 or 400? This too will help with an even cure. Thats what the automotive guys do who have crossed over into spraying instruments. The scuff helps break the skin (think old can of paint) and fully out gas. However, it seems to be a rare practice with luthiers, who seldom hit the last coat with anything coarser than about 800/P1200 grit. BTW - I go 2 weeks cure for maple instruments, 3-4 for anything porous (Koa, Mahogany etc). |
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| Author: | B. Howard [ Sat Jul 07, 2012 7:24 am ] |
| Post subject: | Re: Nitro Cure Time - Dry Box |
Not all lacquers are designed to be force dried, so you should consult the manufacturers tech dept first. Most commercial force drying is done at 140 degrees F. A good practice for furniture and cabinets perhaps but as Todd pointed out maybe not such a great idea for guitars. Force drying material that is not engineered that way can lead to delamination down the road from solvents becoming trapped inside the coating, especially if solvent blends have heavier retarders in them. Patience is a virtue and good finish work simply takes time. |
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| Author: | bluescreek [ Sat Jul 07, 2012 7:47 am ] |
| Post subject: | Re: Nitro Cure Time - Dry Box |
The common thread to all of this is the you need air circulation. I also feel RH control helps. Patience is also handy. In most cases you will find that 10 days to 3 weeks is not uncommon. Rushing a finish can ruin it so time is your friend. The dry rooms that commercial operations use are similar to what industry may call a white or clean room. Filtered air RH Control . I allowed 24 hrs for the finish to set , then placed it where I had good air flow . I have seen chest freezers converted for this processes . A hole was cut in the side and a filter installed . A small fan was used to induce air and an exit hole with filter on the opposite side. If anything it protected the bodies from getting bumped and did look cool. The exit air was vented to the outside. He used a small ceramic furnace heater as the air fan and could apply heat. |
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| Author: | NWflyonly [ Sat Jul 07, 2012 9:42 am ] |
| Post subject: | Re: Nitro Cure Time - Dry Box |
Thanks everyone! Circulation isn't an issue there's plenty though I don't have a fan it's just out in the open. I know that the longer I can wait the better off but dang I'm pretty excited and want to get'R'done! |
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| Author: | Stuart Gort [ Sat Jul 07, 2012 11:30 am ] |
| Post subject: | Re: Nitro Cure Time - Dry Box |
NWflyonly wrote: ...but dang I'm pretty excited and want to get'R'done! I know exactly how you feel there, pal. I only hope that resanding several guitars will attenuate my impulsive nature. |
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