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curing nitro flammability - after the spray


komodo
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I'm aware of the flammability of nitro when spraying, but can't find anything on this. I've got a temporary booth where I can spray outside but after I spray a coat and it has initially flashed off and then bring it inside to hang - how flammable is it while curing? I've got a largish shop with a strong fan that feeds positive pressure into the room, ejecting through another vent. The fan is made for a sauna and should have enough power for several exchanges an hour, and can be left on indefinitely. The fan is mounted up in the ceiling (was a darkroom), but is not explosion proof, and the shop heater is open flame. I'm really wondering about fumes from curing.

All help is appreciated!

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I think the major danger time is during spraying when solvents and solids are atomized. Curing is a process of evaporating the solvents but it is a slow process. I'd be shocked if there were enough gas created to constitute a hazard from your fan or heater. Unfortunately I do not have any hard data to back that up. Why not create a little experiment with scrap? Spray some scrap and put it in your bbq grill will the top on for a half hour and use something to extend a flame in near it and see if you get any flare off.

Feel free to excoriate me if that is a stupid idea.......:)

SR

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Hahaha I love it. I have a feeling that the results of that test wouldn't necessarily scale up. Imagine the talk with the fire marshall when you tell him you did a small scale test to make sure it was OK. Ha

I think you are right though, and my instinct is that the real danger is in the atomized nitro, not the solvent.

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I think the major danger time is during spraying when solvents and solids are atomized. Curing is a process of evaporating the solvents but it is a slow process. I'd be shocked if there were enough gas created to constitute a hazard from your fan or heater. Unfortunately I do not have any hard data to back that up. Why not create a little experiment with scrap? Spray some scrap and put it in your bbq grill will the top on for a half hour and use something to extend a flame in near it and see if you get any flare off.

Feel free to excoriate me if that is a stupid idea.......:)

SR

Fire is caused by oxygen, fuel and ignition. Reduce or eliminate one to below the requirement for a fire and you're okay. If the fan is brushless and doesn't cause sparks then you should be good. I'd simply just allow it to offgas without forcing it. I'm sure that applying direct heat will cause more skinning and solvents to be trapped?

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I'm sure that applying direct heat will cause more skinning and solvents to be trapped?

I think so too. But I'm sure I read a post by Perry Ormsby a few years ago that said he had a heated room to speed up the curing on his clears. I thought he was discussing nitro.....but can't swear to it.

SR

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A heated room is not the same as directly applied heat. With a higher ambient temperature, there is less of a gradient between the workpiece and the air. As I understand it (finishing is not my area) this is quite different. @demonx or @Robbinst might be a better source of answers in this regard.

I'd certainly be wary about leaving it unattended. You really don't want any potential sources of fire. 

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