Frist and formost, if you spray catalysed clear at 50 degrees it will NOT cure . it must be at 60 degrees for at the very least 48 hours to crosslink properly. if you cant get the sprayed airframe up to 60 degrees for the needed time, you should not even consider using catalyzed clear. Dope does not require this temperature to dry. it can dry at much lower temperatures because it does not need to crosslink it just needs to let the thinner leach out. If you decide that you can maintain the temp, then you need to find out what brands are available to you localy. I prefer PPG clears personally
A few other things to think about, you need to insure that you have positive airflow for quite a while after you spray. You also need to take seriosly the toxicity of this material. appropriate respirator, skin covered, and eye protection. If Urethane is applied correctly I have not seen any tendancy to crack, Imron was very brittle and it would crack if there was any flexing.
as for the gun and tip size, you cant judge by tip size, its all about the way the gun is configured. Any good hvlp will work though a larger fluid flow will be problematic if you arent used to spraying this material. In other words, more prone to runs. Myself, regardless of what clear I use, i typically will reduce slightly more than what the manufacture recommends. The recommendations published are based upon the VOC standards not necessarily for optimum spray ability. From there its a matter of experimenting with your equipment to optimize the spray pattern of your gun. What kind of gun do you have?
One other thing you will  need to be aware of is that Urethane tends to flow after you spray it more than Dope will.
This is about all i got for now, its late and I am cranky lol, Randy, you can take over from there, Randy sprays his where it may be cold, but he can bring his in to the warm house after it flashes off so it can cure.

Clint,

I have used Omni MH 162 clear. It's pretty decent stuff and not horribly expensive. I've shot it as low as 45 degrees (I shot the stuff outside), then take it into the shop. From experience, I can tell you that it needs to be in an environment of at least 60 degrees at least until it catalyzes (maybe 6 hours). I've shot the stuff and got it into a fairly warm shot, but then turned the heat off and left. It was pretty cold in there the next day, but the stuff was dry. In the cold it does take longer for it completely harden.

This is just may experience. Mark knows more about this than me, so listen to him.

Seriously thinking about skipping the 8 coats of clear dope on this Playboy and going with an auto-clear finish. Of course the color coats will be Brodak dope over Polyspan and Silkspan.
Got a few questions: Is the auto paint more prone to cracking? Can plastisizer be added? My spray temps will probably be in the 50's. Is that too cold? What is a good brand or what EXACTLY should I ask for? My HVLP spray guns have a 1.4 and 1.8 nozzle. Which would be better for this type of finish? What about air pressure?
I'm sure I'll think of more questions. Thanks in advance.

8 coats Clint!!!!? I seldom use more then 2.

Keep in mind this clear does not "dry" ,, well it does dry, but that's not what gives it any strength, it has to cross link chemically which occurs as a result of the chemical reaction. I have seen Randy's stuff, and he does good,, the Omni is a slightly higher Acrylic content, which for production car work isn't the best thing, but on our planes it just happens to be a good thing as it renders it slightly more flexible. It is also cheaper than the clear I use. Randy, well, I would strongly recommend longer than 6 hours, but at least that's  better than none. Tho other caution is that when you bring it in from the cold after spraying it, it can move again on you, in other words runs,, If you have it on a paint stand you can rotate it every once in a while to chase the run back over itself.

I'll check on the Omni paint availablity here. I don't have a rotating paint stand (and really can't afford to run out and buy one right now). I usually hang the plane and shoot it from all sides, so runs could be a problem. Is there a way to get to harden faster?

Clint,
I will be as tactfull as I can, but I have to be blunt,
shooting urethane clear to some extent requires that you make some commitments. One is the cost of the material, another is the recognition that this is NOT dope and as such has some constraints that you must adhere to. Yes you can accelerate the clear some, using faster reducers, faster catalysts, or higher temperatures. However, good gun technique trumps all of the shortcuts. If you plan on using this product, you are just going to have to make some decisions. Practice is paramount. i would definitely recommend that you spray something you dont care about first. heck paint a desk lamp, or a wastebasket, something! You are taking a huge risk to just grab the gun and go on your stunter that you spent all that time building. I know you probably already planned on doing some practice, but I just want to make the point, this can be a real disaster if you start painting without first practicing. to accelerate the product you will make some compromises, first is the integrity of the film. second, if you accelerate it you can cause it to shrink and orange peal more profoundly.
In short, the best way to avoid runs is not by speeding the product up, but by learning how to spray it with your equipment until you are comfortable that you can lay down a wet film with minimal dry edges, and runs.  i guess one of the reasons I get concerned for people spaying urethane the first time is that its very hard to reverse any mistakes. Once the clear kicks, and hardens, it gets much more difficult to fix, especially over open bays.
i hate to sound doom and gloom. its not that hard to use actually, once you get a feel for it. I encourage you to explore and get comfortable with it. It is a real step forward for longevity and durability on your plane. Just learn the differences before you go gun happy on your new pride and joy.
A few more details,, with an HVLP, more pressure isnt always the best answer. I prefer to  use just enough pressure to atomize the clear effectively. Atomization is one of the keys to getting it to lay down and flow, with a quick enough "freeze " time to prevent runs. When I shoot my planes, I tend to overreduce by about 20 percent. so, if the mix is 4 to 1 to 1 part reducer, i will normally go with something like 4 to 1 to 2 parts reducer. then I will adjust my gun so that the fan is even and well atomized. My technique for this is to hang a piece of masking paper on the wall, with the fan turned horizontal so it sprays left and rght, hold the gun the proper distance away from the surface and pull the trigger. spray until the clear begins to run down the paper in rivulets  and stop. The rivulets should be uniform across the entire distance of the pattern. Adjust the pattern until these rivulets are evenly dispersed across the pattern. If it is to light on the edges, it may be that you need less air pressure, you just have to experiment. All guns are machined differently and have different setups, kind of like stunt motors. You just have to play with it until you find what works with your guns. The Finex guns are a really good inexpensive gun. One really important thing with them is that for some reason, they are very sensitive to any residue. You really need to be thorough when you clean it or it will compromise the spray pattern. Oh while I am thinking about it, the proper distance to hold the gun away from the surface is approximately 1.5 to 2 times the width of the pattern with most guns. Its a good starting place in any case.
ok well thats all i got now, i hope some of this has been productive and given you some valid information to work from. If you want more, let me know and I will see what I can come up with.

Clint,

Only advice I can give on top of what Mark has said is, go easy with it. The stuff runs pretty easily. While runs can be corrected, why get them? I usually shoot a light dust coat, let it dry for a bit (10-15 minutes - until it gets tacky) then shoot on a medium coat and leave it.

Mark, good description.

What happened to the Cougs?  (OK, that was a dig, but I get them so seldom...)

Clint,
glad I came across right,,, What randy says about the tack coat is valid,, but dont be misguided by thinking you need to wait the whole intercoat dry time,, the tack coat will help suck the solvents out of the flow coat and help prevent runs. so shoot your tack coat,, then come back and put on your flow coat, i pretty much use one coat of clear, but then I dont typically cut and polish my clear very much. More just dirt nibs. you may try also when you get ready to spray, setting up a bright light across from where you are spraying so you can get a good glare across the surface you are spraying. I would also say, i built a spray jig like what Randy describes, really easy and so so much easier to paint on. hanging parts or planes to paint them is a pain. It sucks to chase the thing around while you are trying to lay down a controlled even layer of clear!

I attached a picture that shows part of my paint stand. well actually its a picture of my Avenger,, but It is in the corner of my bench holding my bf 109 stunter. it is standing upright now,, but it also clamps down flat so the dowel is horizantal so you can work on it. i just clamp it to the bench  with a c clamp hanging over the edge. There are two bulkheads and a base, the bulkheads have one inch holes drilled in them, and the dowel just rotates in them.   The end  inside the plane has a flat machined onto it, and two holes. then I have a 1/4 inch flat plate that bolts where the motor attaches then it screws into the dowel by the two holes.
sorry this is the only picture I have of it, i stole the  idea from Bat man Randy,, fortunatly ,mine has generated no attraction to bats or lollipop green airplanes,, grin,,

Randy dont be doggin on my cougs!!!! do you have any idea how hard it is to recruit people to come live in the snow and cold!

to further hijack the thread,, just remember,, there was something called the apple cup this fall? yeah i thought you would forget that one!

Its all about the sequence you spray it in. Also  using the appropriate reducer , I usually will use a reducer that is one step slower than the recomended one by the manufacture. This keeps the surface open and receptive to the overspray melting in.  I try to start at the nose, spraying all the way around the nose, down the top of one wing, and back up the bottom, across to the other wing, and then back on the top. then you work down the fuse, and do the tail the same way you did the wings. Good control of your clear is really important. you need it to flow, but not run. Its a tightrope to get it right. Hence your spray gun settings are really important,and the accuracy of your pattern distribution is critical. Also the distance and overlap of your passes is very important. Ok so everything you do from the time you mix the clear till you clean the gun is important I guess? One trick you can use, at your own risk, is to have another gun with the very slowest reducer made for the product. After you spray your airframe, you can go back and overspray the dry spots with a light coat of reducer to help it flow. THIS IS RISKY AND YOU TRY IT AT YOUR OWN RISK!!!!! but, its a last resort. It is better to get it laid down right the first time. A dry spot, is easier to fix than a run on something fragile or soft like a open bay wing. Remember, this clear, at least most brands, will continue to flow after you spray it so some experimentation on something that doesnt matter is really valuable!

Hi Gentlemen,

I notice a beautifully crafted plane over at the other site.  He used transparent monocote or some other film on the wings then he mentioned he was prepping for clear with a automotive brand I don't remember what it was.  My question is was he clearing the film,(compatibility problems?) also, and if so what happens in time when the film loosens are is exposed to the sun sometimes and wrinkles. I'm ready to finish three planes and was going to monocote the wings and paint the fuse etc. and was just going to clear the painted area. Is there some benefit to clearing the film?
Thanks,
Tom

Basketball, did they finally got bribed into finally thinking  that is a sport?  hmm I thought it was just some guys chasing some round ball around,, and something about a peach basket???

I have heard of guys clearing over film, but mostly its been over Ultracoat, not Monokote, or sometimes over Micafilm as well. Tom, do you have a link for the thread your refering too? is he maybe clearing over tinted dope on silk ?

Thanks, yeah i looked at it, It really enhances the gloss of the film. I suppose if you were to abrade the surface lightly, and clean celan celan, it may be alright. Not sure that with my experience I would trust the film to stay tight though. Especially with the huge variations in temperature we fly in?
I must say though Allan is respected and I would hope he has done this before.

Terry,
trust me, sensitivity is part of the problem. Toxicity is the worst part of the problem. This stuff is catalyzed by Isocyanates, that is a cyanice derivitive! It is carcengogenic, and accumulates in the body never leaving . Yes this does build a sensitivity, but trust me, it is TOXIC and it will KILL you if you dont respect it. Now, if all you do is paint model airplanes, then unless you dont take any precautions its not likely to kill you, but it will damn sure make you sick as heck.
On another note, flex additive does not do what you may think it does . the typicall scenario is that a painter will add flex additive to a soft bumper, this does help keep the paint more flexible for AWHILE, it eventually, over the course of a few weeks, evaporates, or otherwise leaves the paint and does not enhance the flexibility from that point on.  The intent of flex additive is to enable the body man to reinstall the flexible part on the car without cracking the clear. What is does do is degrade the film strength by adding "contaminants" to the resin matrix. It also slows the catalyzing of the clear. Anything you add to the resin binder matrix, degrades the film integrity to some extent. Some of it not appreciable, some of it is.
This information is from several PPG training schools I have attended.
I hate to make my case, but I have been a profesional painter for a few years,, lets round it off to say about 25 or so shall we? I have attended schools, safety seminars, and have sprayed this material a fair amount. Please take the warnings serious, read the MSDS if you dont believe me,, actually read it even if you do beleive me. This paint is serious stuff, but its no more dangerous than walking across the street,, but, just like walking across the street, if you dont check to make sure that no  buss is coming, well, you may well get run over!

  SAD THING IS...IN TRUTH!!!! So few of those exotic painters who didn't follow the strict directions to the letter where I worked at Boeing are still alive to tell the NAKED TRUTH about the toxic nature of those new exotic paint fomulas~~~
Last month we lost one of our most gifted Boeing Phantom works display model painters and custom car painters.
Rich Moran...he's flyin with the angels today.

Well I appreciate your profesional perspective. So you are telling me that Isocyanates are not lethal? I might dissagree. At the very least, the VERY least, the quality of life will suffer greatly including use of oxygen, and debilitating lung damage. However, I will not dispute you on that. When it comes to my experience i would rather this exchange had taken place off forum as to not cause an issue. But since its here, From my perspective I may tend to overstate some of the issues with products because the hobbiest tends to not to take things serious because "everything is toxic" and they dont use it as much as a proffesional, so what the heck. I would much rather overstate the dangers of these products than to make light of the serious nature of exposure. If I read your reply, to me it does just that, it makes light of the very serious nature of exposure to these products. I also dont quite understand why you are disputing my use of the term "toxic" when you later state that every thing can be stated as toxic. Of course the same could be stated for epoxies which are also proven to cause sensitivity problems. I will state again, I will not dispute your professional experience however I will strongly disagree with the manner you presented this information because it feels like you are saying this material is not that dangerous. that really concerns me.

upon further thinking, I feel clarification of my position is in order
Let say I come on here and say if you aren't careful you can cut your finger off if you use and APC prop,,
then you rebut me by saying, the proven incidence of actually losing a finger from an apc prop has not been proven,, it takes some amount of energy to sever a finger, and the prop cant generate that.

Your response would be perhaps more factually based,, however does it accurately reflect the danger? I think it understates the danger, whereas my response, while perhaps not absolutly accurate , does more accurately get the point across that these props are NOT to be taken lightly. My conciense is clear for having perhaps overstated the danger,, however if I took your position and someone gets cut and permanently damages nerves and tendons because they didn't take the danger serious enough, I would feel guilt. What I am saying is, sometimes facts are more dangerous than a simpler statement of the dangers.


as to this,
*****Now the stuff on the lex agents is good to know.  I thought they increased flexiblity of the coating over the longer time span.  I know that hitting a plastic bumper years after it has been painted doesn't crack and peel the paint as badly as on metal.*****
If you observe the bend radius on a metal fender where the paint delaminates, and the bend radius of a flexible bumper when you hit it,, I think you would find it is much more likely that the bend radius is the cause of the paint failing at the bond than the flex additive is. Oh and this information comes from the PPG training seminar.

Whether you use the term toxic or hazardous, the fact remains that this stuff can be dangerous. I think the comment about sensitization is a good one. I became sensitized to catalyzed polyurethane (Imron) some 15 years ago and now I have to be careful with the stuff. A good respirator (I talked to 3M and they suggested a type of filter that will trap isocyanate), long sleeves, gloves and and hat with goggles and I shoot the stuff outside. I wear this stuff from the moment I crack the can till I put the plane in the shop and close the door and walk away. Weirdly enough, once catalyzed, I have no problem with it (such as sanding dust from the catalyzed finish). But at least for me, the smallest amount wet is bad news.

Toxic and hazadardous are different terms.  Toxic means that in some concentration, the material can cause adverse conditions.  As I said, oxygen is toxic.

Hazardous defines that in the current situation the material can cause adverse conditions.  Oxygen is only hazardous if you are exposed to a partial pressure of oxygen of 30 psi or greater. 

So oxygen is toxic, but it is not hazardous to you sitting reading this. 

Here is a link to the PPG Omni MH167 fast urethane hardener: http://www.pcsscreston.ca/MSDS/MSDS1/PPG/MH167.mht

It contains HEXANE-1,6-DI-ISOCYANATE POLYMER and ISOPHORONE DIISOCYANATE POLYMER.  If you read the exposure limits there are no ACGIH (American Council of Governmental Industrial Hygienists) or Ontario exposure limits.

If you read the toxicity data, you will see for both compounds there is no info available.  So hard to say it how toxic it is when there is absolutely no data.

There is an IPEL-TWA of 0.5mg/m3.  That is based on an 8 hour time weighted average.  Which is an average exposure over a full 8 hour work shift.  There is no STEL specified.  Although there are rules of thumb about not exceeding a multiplier of the 8 hour level.

Now, you also need to understand that 8 hour TWAs are set based on various criteria.  For carcinogens, it is based on a 8 hour a day, 5 days a week, for 70 years.  So a hobbyist exposure is unlikely to cause problems.

For others, it can be acute effects.  But without any toxicity data, it is unlikely to be based on acute effects.

And looking at the overall symptoms of overexposure for the mixture, you see that the effects are hedged with terms like long term exposures, and high vapor concentrations.  And the effects are more irritation effects.

As a professional, I HIGHLY recommend taking precautions when using isocyanate containing products.  But the attitude that you are going to die if you breath even a tiny amount of the material is also not realistic.  If you take this attitude, even a hobbyist will need a full positive pressure supplied air system, since there are no filter respirators that reduce isocyanate exposures.

In fact, as a professional, do use a true positive pressure supplied air system?  And a positive pressure supplied air system is one that supplies your breathing air at above atmospheric pressure, similar to the units used by fire fighters.  NOT blowing air into a loose fitting hood.  And that is what the MSDS recommends.

And, as said before, most of the issues with acute effects are from people who have already been sensitized.

In fact, I am more concerned, in many cases, with the solvent exposures from spray paint operations.

No problem.

Also, brush finishing urethanes are not a big deal.  They have very low vapor pressures, so not alot of evaporation.

Spraying of course, can put a lot of material in the air.  But again, with the low vapor pressure, it is caught up in droplet form.  And while you should be wearing respiratory protection, droplets are typically caught by the bodyies natural forms of protection (nasal hairs, nasal mucous, etc.)  So they they normally don't penetrate far into the lungs.  I also wonder how much binds up during the induction time and thus is not available to evaporate.

Of course, the solvents used have very high vapor pressures and so are present in pretty high concentrations as vapors, which do penetrate deeply into the lungs where they are absorbed.  If you pay attention, after exposure to solvents, later, you can continue to smell the solvents, but when you exhale, meaning your body is expelling some of them via the lungs.

Painting outdoors (for hobbiests) or in a proper paint booth (for professionals) is a excellent way of controlling exposures.  Best way to reduce exposure is to reduce the concentration in the air.  HVLP guns, properly adjusted, also help with this.

If respiratory protection is used, as I have said before, standard paint spray respirators do not stop (heck they hardly even slow down) isocyanates.  But they will stop most droplets and of course will reduce the solvent exposure.  But you do need to change the cartridges on a regular basis, even if you don't use the respirator as the cartridge will absorb chemicals from the air.  And if while spraying, you ever smell the solvents, stop and change the cartridges.

One problem with many solvents is their acute effect is narcosis. IOW, exposure can make you drunk.  Which makes you think you are invincable, and therefore do more stupid things.

If you are a professional, you should have proper fit testing performed at least once a year for any tight fitting facepiece respirator.  This will include challenging the fit with some benign agent to determine if the fit is proper.  Commonly used challenges include saccharin, irritant smoke, or ethyl acetate (banana oil).

For a hobbiest, the best you can do is a fit check (which everyone should perform, EVERY TIME they put a tight fitting respirator on).  To do this, don the mask and adjust the straps (if using paint spray cartridges with a prefilter, you may need to remove the prefilter).  Using your hands or some plastic (sandwich wrap/baggie if fine) cover the faces of the cartridges and breath in.  You should not hear or feel any air getting into the facepiece.  The face piece should collapse slightly.  If you do, determine where the leak is and adjust the respirator or repair the area leaking.  The next step is to seal the exhaust valve with the base of your hand and gnetly breath out.  You should feel the facepiece inflate slightly and no air should leak.  Of course, you can blow out hard enough to break the seal, so a gentle exhalation is used.

And again, we are exposed to a lot of hazards in our life, and while I do not want anyone to think tha isocyanates are something to be taken lightly, they are also not a magic bullet that will chase you down and kill you.

As an aside, an interesting thing.  Since the rise in HIV in the world, the number of health care workers coming down with hepatitis has plummented.  People are so afraid of HIV, they are actually taking the precautions that are protecting them against many other diseases.  And Hep is much easier to catch, and has some serious consequences.  So the boogey man of HIV is actually doing some good.

Isocyanates, IMO, are similar.  But professionally, I don't use teh boogey man approach unless nothing else works.  I find treating people like adults and properly informing them works better, most of the time.

Clint,

Back to the actual question. I use Omni 2 to 1 clear. It's pretty forgiving stuff. Very easy to shoot. Depending on conditions, I use a bit of urethane reducer in it. When the temp is in the 65-80° range, I just use the paint and hardener, mixed 2 parts paint to 1 of hardener just like the directions say (be sure to get an MSDS sheet when you buy the paint). I've shot the stuff in temps as low as 45°. You really kind of have to reduce it a bit to get it to flow in lower temps. In those sort of conditions, I use 2 parts paint, 1 part hardener and 1 part urethane reducer and it works alright. But shooting in such low temps can be tricky. And you really need to get the plane into a warmer environment to cure.

The clear I use is Omni HiSolids Clear MC161. The hardener comes in several temps. I tend to use the slowest all the time because I get better flow and reduced orange peel, but I imagine if I was shooting it in 90+° temps, I would look at some of the faster hardeners. Maybe someday.

Fast Hardener is MH162, the Medium is MH163 and the Slow is MH164 (the one I use). Most any pPg urethane reducer seems to work OK. Right now I'm using Matrix MR-0800 Series Urethane Reducer. But it's just because it's what I have at the moment.

Just mix up the paint (with paint mask on) and add one part reducer if it's colder than about 65°. Then mist a coat of clear over the main airframe. Do the same with the parts (flaps, cowl, etc.). But the time you get that done, the mist coat over the main airframe should be tacky. The go back and shot a nice, medium coat of clear over the main air frame and the same for the parts. Try not to go back over areas that have been shot. It reduces (no pun intended) the chances of getting a run. Then put the plane in the hopefully warm shop (don't touch the paint) and let it sit for 24 hours or so.

For me, I try to sand the plane to a matte finish after 24 hours. The paint is a bit softer and comes off easier. I use 800 used wet (water with a few drop of dish soap) for the rougher spots and overall with 1500 wet to level the finish (hopefully, it's alread pretty level). If you wait much past 72 hours, it's pretty hard and getting it flat (more likely to sand through the clear over ribs and such)  can be a bit trickier. It can be done and I've done it, but it's harder. After you've sanded it out to a matte finish, let the thing sit for a couple of days (until the paint is completely cured - this time can vary depending on how much, if any, reducer you used). Once it's really hard, you can go back with rubbing and polishing compound and bring up a lustrous finish.

Hope that actually answers your question. I went and looked up the paint numbers in my shop since I could remember before.

Good luck with it and ask if you have any questions.

Mark,

The problem is, many of those sources state that it is toxic, but without any toxicity data. 

As for the NIOSH quote, it is saying excatly what I said the first time, it is a sensitizing agent that once a person is sensitized, they have severe adverse reactions to further exposure.  But prior to beig sensitized, it is mainly an irritant.  BTW I even included that quote in a previous post.

And I never said to not take precautions, just that it wasn't as hazardous as you made out.

BTW I discussed this with several professional colleagues after the last posting, and all (with a combined experience as occupational health and safety professionals of over 100 years, all professionally certified) and they all agree with me.

You paint for a living.  I protect people from exposure to hazards.

BTW what personal proective equipment do YOU use when spraying isocyanate catalysed paints?

>>The problem is, many of those sources state that it is toxic, but without any toxicity data. <<

Well, pop a can open, stick your nose in and take a deep breath. Trust me, you get all the data you need.

OK, that was snotty. Sorry. But I think the point was to not to soft pedal the dangers. This stuff ain't lacquer. I'm probably a bit touchier than most about this because I AM sensitized. I had one exposure (first time using it) that put me in the hospital on a ventilator and have had to be very careful of the stuff since then.

One point I find interesting. You said earlier that there was no filter based mask that was effective with iso-cynates. I talked to a 3M rep that said that they did have filters that worked with the stuff. I'd probably take your word over his, but I think it's interesting that 3M would say this.

I will have to check with 3M at our professional conference.  But the last time I checked, no filter based product.  In fact, that is one of the problems with trying to actually measure exposure.  For normal solvents, we suck air through a glass tube packed with activated carbon.  But isocyanates are not hardly slowed by activated carbon, so you just pump it through the pump.

Also realize, that a properly fitted (and how many people have ANY idea what that entails? ) half face mask has a protection factor of 10.  That means it only reduces the exposure by 90%.  Also filtering facepieces are only acceptable (from workplace) with materials with good warning properties, ie you can smell them at concentrations much lower than harmful.  And since you can't smell isocyanates themselves, you should never rely on filtering systems.

BTW from 3M: http://multimedia.mmm.com/mws/mediawebserver.dyn?6666660Zjcf6lVs6EVs66SNWDCOrrrrQ-

Notice the NOT on filtering facepiece respirators. ONLY supplied air are deemed acceptable.  Other references from their site specifically state to not use various air purifying products with isocyanates.  Again, you have no warning if the filtering breaks down.

There are similar issues with methylene chloride.

And one thing in this thread that REALLY bothers me is the idea that non-isocyanate paints are benign.  They AREN'T. Many of the solvents used are neurotoxic and have both acute and chronic exposure issues.

How about a chemical with these warnings:

DANGER! HARMFUL OR FATAL IF SWALLOWED. HARMFUL IF INHALED OR ABSORBED THROUGH SKIN. AFFECTS CENTRAL NERVOUS SYSTEM. CAUSES IRRITATION TO SKIN, EYES AND RESPIRATORY TRACT.

Causes irritation to the nose and throat. Concentrations above the TLV may cause headache, dizziness, nausea, shortness of breath, and vomiting. Higher concentrations may cause central nervous system depression and unconsciousness.

May be absorbed through the skin with possible systemic effects.

Chronic exposure may cause central nervous system effects.

Persons with pre-existing skin disorders or eye problems or impaired respiratory function may be more susceptible to the effects of the substance.

Has shown teratogenic effects in laboratory animals.

Pretty nasty stuff?  Stuff you wouldn't want to expose yourself to?  Stuff you want handle with extreme caution?

The quotes are taken from the MSDS for simple MEK.  Used in most laquer thinners.

I only use the gov standards when I have to have a tool to beat someone over the head with.  Otherwise I go with best practices.  There are issues with standards.  1)  For a sensitizing agent, they have to try to protect the sensitized person, which may require VERY low exposure levels that are not needed by everyone.  But you do want to prevent people from being sensitized.  But each persons threshold for sensitizing is different.  2)  People assume that if you are below the limit you are "safe."  But the the standards are based on a cost benefit ratio and will NOT protect 100% of the population exposed to that level.  This also means that if you are above the level, you are not necessarily not safe, it depends on the individual.  3)  Standards are based on workplace exposures, which are based on 8 hours per day, 40 hours per week, 50 weeks per year exposure.  For most chemicals, shorter durations per day or week reduce the risk, and allow higher exposures.  It depends on whether the chemical is cleared from the body and how fast or slow that clearance is.  Of course, with some chemicals, there is a threshold for acute effects.  Isocyanated in a sensitized individual is one.  It also means, if you are exposed for longer periods, the "safe" exposure may not be safe.  With some, there is a question if dual shifts can safely use 1/2 the 8 hour exposure rate due to the reduced time between exposures.  But in general, hobby exposures are short duration.  You paint 1 plane, not 10 cars.

It will be interesting if they have a filter that will last 45 minutes.  Previously the breakthrough time was measured in seconds.  If you can get the part number, that would help.

Yea, that is the problem, people have been working with something for 20 years and they are still alive, so it must be safe.   My profession is to work myself out of a job, but I am not worried.   But have you been hospitalized due to urethane clears? 

Yeah, the second and later exposures are what are REALLY nasty.

But it doesn't sound like you are truely sensitized, since you can be around it at all.  First time I saw my friend, who is sensitized, get about 100 yards from a urethane spray operation, he turned red, had trouble breathing, and was in bad shape.

But be VERY careful. 

The wierd thing about sensitization is that each person has a personal threshold.  And as long as you don't hit that threshold, you are fine.  But once you do, you are changed for life.

The body is a strange thing at times.

Donnie,

Yea, I'm qualified now, but back then...  The warnings are on the cans, you just have to read them. Instruction sheets are readily available at the paint shop. Why should they not be available? It's my responsibility to READ THE CAN AND INSTRUCTIONS then take precautions and use the product as instructed, not the manufacturers responsibility to be my nanny.

Mark and Pinecone, I thank you for the above discussion.  I shall take that paint a whole lot more seriously now.