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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Body - Exterior> Paint> Urethane vs Arcylic enamel with hardner
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Topic Review (Newest First)
09-12-2019 06:07 AM
dwighty390
Quote:
Originally Posted by idrivejunk View Post
If using supplied air, you don't smell them.

Isocyanates love eyeballs, I know that. Easy way to sneak in on guys with half masks.
Yep, I can't wear contacts anymore and I blame it on isos entirely.
09-11-2019 11:08 PM
idrivejunk
Quote:
Originally Posted by dwighty390 View Post
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.

Isocyanates love eyeballs, I know that. Easy way to sneak in on guys with half masks.
09-11-2019 12:41 PM
dwighty390 Splitting hairs indeed, I was just stating a fact that they are NOT odorless.

The doc also says "typically" and "probably."
09-11-2019 12:39 PM
John long 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
09-11-2019 12:26 PM
dwighty390 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).
09-11-2019 12:24 PM
dwighty390 No way. Iso's are what give the sweet smell.

3M does actually mention that one, interestingly.

https://multimedia.3m.com/mws/media/...techupdate.pdf
09-11-2019 12:21 PM
John long
Quote:
Originally Posted by dwighty390 View Post
You're right, 3M doesn't specifically call out iso's.

Iso's DO have a smell, however.

Paint smells. Isocyanates do not. Matt is correct.

John
09-11-2019 12:13 PM
dwighty390
Quote:
Originally Posted by idrivejunk View Post
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.
09-11-2019 12:01 PM
idrivejunk
Quote:
Originally Posted by dwighty390 View Post
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.
09-11-2019 11:49 AM
dwighty390
Quote:
Originally Posted by idrivejunk View Post
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...
09-11-2019 11:41 AM
idrivejunk
Quote:
Originally Posted by dwighty390 View Post
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.
09-11-2019 10:56 AM
dwighty390 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.
09-11-2019 06:54 AM
idrivejunk 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.
09-11-2019 06:46 AM
idrivejunk 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.
09-11-2019 06:16 AM
John long 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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