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The Penny Pincher
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I don't know any reason anyone would use an enamel instead of a urethane.
Urethanes are far superior in every way.
Most clear coats over base coats are urethanes, just without color.
They are night and day difference on hardness.
Enamels, even with hardeners stay really soft a long time, urethanes
can buff easy the next day, they harden fast.
I use to buff out enamels with hardeners back in the 1980's,
I would never go back to that with urethanes available now.
I did my boat and trailer with urethane and it's been amazing
how hard it is to scratch or chip. Probably the most durable paint out there.
 

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Slow but willing learner
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5,333 Posts
I can't argue with that. I have not shot any acrylic in decades. The urethanes are superior for sure.

John
 

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Grand Prix user
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5,407 Posts
What a confusing read! Acrylic lacquer replaced nitrocellulose lacquer. Acrylic enamel replaced alkyd enamel. Acrylic urethane replaced polyurethane. Lacquer dries by evaporation only, enamel dries by that plus oxidation (and curing, to some degree, if isocyanates are added) and urethane by evaporation plus molecular crosslinking when cured. Lacquer rubs off with thinner. Enamel does too, but takes more rubbing. Meaning both of them can "re-wet". Urethane cannot, it turns to plastic when cured.

In my humble and obsolete opinion, if doing a car... cheap urethane beats enamel with all the bells and whistles dumped in. By a long shot. Thats is not meant to indicate theres no place for enamels. Just not for the exterior of anything I want to keep.
 

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Grand Prix user
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One more thing... no amount of filtration is protection from isocyanates. Fresh, supplied breathing air is the only escape, and must be in conjunction with full body and face protection.

Danger is not in standing on a cliff, it is in being unwary there.
 

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290 Posts
Enamels are significantly cheaper and slightly safer for a hobbyist without the fresh air supply. For something that isn't going to be weathered, I see no issue with them. E.g. if you are restoring grandma's steel China cabinet or something, they'd give great results.

The proper masks used properly will work but you do need to keep the air in the booth clean - this is how I have seen most body shops with downdraft evacuation operate. Using the mask in a garage where you are standing in a fog is a huge disaster waiting to happen. I did it for years before finally having a close call and I'll never go back after that.
 

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Grand Prix user
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Enamels are significantly cheaper and slightly safer for a hobbyist without the fresh air supply. For something that isn't going to be weathered, I see no issue with them. E.g. if you are restoring grandma's steel China cabinet or something, they'd give great results.

The proper masks used properly will work but you do need to keep the air in the booth clean - this is how I have seen most body shops with downdraft evacuation operate. Using the mask in a garage where you are standing in a fog is a huge disaster waiting to happen. I did it for years before finally having a close call and I'll never go back after that.
Your first sentence puts it well. And you make a good point about concentration levels. The fact remains that charcoal filters do fine with dusts and some mists... but little or nothing with vapors.
 

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Your first sentence puts it well. And you make a good point about concentration levels. The fact remains that charcoal filters do fine with dusts and some mists... but little or nothing with vapors.
How little? The 3M cartridges mentioned before are labeled specifically for vapors/paint. That would be a pretty big misprint from a pretty large company to be sued...
 

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How little? The 3M cartridges mentioned before are labeled specifically for vapors/paint. That would be a pretty big misprint from a pretty large company to be sued...
Vapors can contain isocyanates or not, as can the paint. So that can be true. You won't find anywhere that says a 3M halfmask is safe for use around topcoat catalyst / hardener / activator. Its a hard line. Isocyanates mean full body protection and supplied air in any case. Its up to the user to manage their exposure, but the isos have no smell or color, so that is at one's own risk.
 

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Vapors can contain isocyanates or not, as can the paint. So that can be true. You won't find anywhere that says a 3M halfmask is safe for use around topcoat catalyst / hardener / activator. Its a hard line. Isocyanates mean full body protection and supplied air in any case. Its up to the user to manage their exposure, but the isos have no smell or color, so that is at one's own risk.
You're right, 3M doesn't specifically call out iso's.

Iso's DO have a smell, however.
 

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Interestingly, this document alludes to what a lot of people say about the charcoal filters for iso's: They work but since they aren't idiot-proof, no company will advertise it as such (they get saturated and become ineffective).
 

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Slow but willing learner
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There will be NO ODOR until you are already over exposed. From your own document you posted.

"The odour threshold for isocyanates, i.e. the level at which an individual can smell an isocyanate, is typically higher than the allowed exposure limits. In other words, if a painter smells the sweet, fruity, pungent odour of an isocyanate, they are probably already overexposed. "

This subject is way to important to be splitting hairs on odor. The bottom line is you CAN NOT rely on odor to decide if your mask is worn out. You will not smell it before becoming over exposed.

John
 

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Grand Prix user
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You're right, 3M doesn't specifically call out iso's.

Iso's DO have a smell, however.
If using supplied air, you don't smell them. :D

Isocyanates love eyeballs, I know that. Easy way to sneak in on guys with half masks.;)
 
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