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Dear Rick (and All),

You made a brief comment, in the "poly vs. nitro" thread, about experimenting with acetone and butyl acetate vs. MEK in your sprayed polyester applications.  I'm curious.  Did you try several different mixtures of the two?

I can understand why acetone might flash off too quickly, while butyl acetate is pretty slow going, but I'm wondering if there isn't a "magic" combination of the two.  The reason I ask is that the long-term exposure to acetone is somewhat less risky than for MEK, even though both are acute CNS hazards.  Did you also consider ethyl acetate?

I've also wondered for a long time why so many nitro solvents still have aromatic content.  Doesn't seem necessary.

Thanks,

-Ben

I can add that I did try acetone, as well as polystyrene. It wasn't until I gave-in and tried MEK that everything worked in harmony. The other solvents create random pin holes, for some reason.


But go ahead and try....

The best solution is to completely protect yourself, instead of trying to avoid the nasties.  From the supplied air hood system, to my clothing, to the double gloved hands, I am completely and 100% sealed from any exposure in the booth. Bring on the MEK!

Now that would be a great picture to see Mario. Space Man Spiff indeed.

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Hey Grumpy, nice avatar...never noticed it before.


Obviously, the biggest hurdle we have with finishes is that the better ones are hazardous to your health. So as Grumpy says, limiting exposure is the best way to deal with them. In order to completely eliminate them, you have to go to waterbornes, which just aren't there yet. In the meanwhile, a really good spray booth, and a way to seal out the hazmats is the way to go.

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Thanks for the replies, all.  To clarify, I was thinking about this in terms of long-term product development.  Brainstorming really.

I don't personally use a spray rig (yet), so my question wasn't related to my personal health.  I agree that prophylaxis is the best approach with most of the finishes we have available, but I was also thinking in terms of environmental health.

Acetone and butyl acetate are prevalent throughout the biosphere, as are ethanol, acetic acid, and ethyl acetate.  The more these can be used as substitutes for petroleum-derived solvents the better, IMO.  (Maybe there is a metabolic pathway to MEK that I'm unaware of?) 

In my day job, I use a lot of methylene chloride (i.e. "DCM" or dichloromethane), and I do a lot of thinking about how I can use less of it.  Solvents are tools, and the analogy carries in that not every job requires the proverbial hammer.  Of course, some jobs do....

Best wishes,

-Ben

You can, and Rick and I both do, use acetone for all the gun cleaning, etc... So in the end, the amount of MEK used is tiny, on the order of around 2-3oz per guitar body in my case.

waterbornes aren't exactly 100% safe, either, and in fact, because they seem safe, few people protect themselves properly, and are in more danger than I am.

There are better, more user-effective ways to help the environment.

I agree that waterbornes aren't safe.  In fact, the glycol ethers have worse long-term and reproductive effects than MEK.  I've sprayed plenty of house paint containing these solvents, and the odor also lasts a long time.

2-3 oz. is a very small amount of MEK, especially if it is the magic bullet that gets the job done.  Thanks for clarifying that, grumpy.

Typically, if a person wants to establish a solvent replacement, the task is to triangulate the solubility parameters with three other solvents.  1:1 swaps aren't typically possible.  I thought Rick's comment on butyl acetate in combination with the acetone was interesting enough to warrant further comment if he did blending of the two.  The butyl acetate not only serves as a solvent but as a slow-drying leveler.  Plus the guitar will smell like banana candy.

-Ben

I stand corrected:

I'm still hoping to hear about Rick's experiments whenever he returns, if for no other reason than the shear "geek" factor of it.  However, I had the opportunity to talk with a "real" chemist today.  He explained to me that the biological effects of MEK vs. acetone are not different enough to matter.  The reason MEK is controlled industrially has to do with the formation of ground-level ozone.

I hope I didn't come across as alarmist, or whatever....  Just thinking about little ways to ensure that solvent-borne finishes remain available indefinitely.

Thanks for all the thoughtful replies.

-Ben

I have to disagree with your chemist. MEK is a lot more toxic than acetone.

I should have clarified.  MEK is more acutely toxic to humans and other animals (chiefly through skin absorption), but other living organisms can still metabolize the effluent.

-Ben

I'm kind of back, and all I can say is that Mario has said it.   MEK seems to be the magic bullet for thinning down polyester and getting it to lay down and level pretty darned nicely. I've tried acetone, butyl acetate, ethyl acetate, and MEK just has the right stuff.   I'm thinning the McFadden polyester just less than 25% for spraying, and like Mario, I'm using acetone to clean the gun and keep in the gun between spray sessions even though McFadden recommends against it.   

Welcome back, Rick, people have been begging for your advice.   Hope your trip was a great one, and left you relaxed and renewed, if not jet lagged.

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Thanks for the final word, Rick!  Compared to a lot of other solvents (too many to list), MEK is still a good actor.  You guys are already doing what it takes to minimize it in cleanup, which I applaud you for.  Luthiers bear the torch for best practices within the woodworking industry.

On the whole, today's finishing options are better than ever - regardless of the vehicle.  Of course, we'll always have shellac.

-Ben

"Acetone and butyl acetate are prevalent throughout the biosphere, as are ethanol, acetic acid, and ethyl acetate. The more these can be used as substitutes for petroleum-derived solvents the better, IMO. (Maybe there is a metabolic pathway to MEK that I'm unaware of?)"

Did you know that Bela Lugosi (the origional Dracula) died from formaldehyde poisoning? He was an end-stage alcoholic, ran out of booze, and drank embalming fluid out of desperation. He died on the set of his last movie, and one of the other actor's chiropractor stood in for him, but kept his cape pulled over his face throughout the final scenes.....
Point of story- crazy human beings take a molecule from nature and go cuckoo. If someone wants to expose themselves to toxic solvents, they can do so, but to suggest that MEK, acetone et al may be just a wee bit safer because they are found "in the biosphere" is magical thinking. Our bodies and the life around us did not evolve with these substances in a concentrated, isolated form .
JMHO

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In Markham,Virginia

Jon,

Everything has a dose response.  Even too much water is toxic.  Ethanol is quite toxic to every cell in our bodies, and yet most people can tolerate a surprising amount of it.  Acetone presents us with a narrower window between intoxicated and dead, but there is a window.

Formaldehyde is one of those things that nobody should have any exposure to, yet it emanates from virtually every laminated wood product on the market.  No magical thinking is required to understand that at acetone is present in our bodies from ketosis, while formaldehyde is an industrial pollutant. 

I take your point that concentration can drive things out of balance with any substance.  Even orange oil isn't safe enough to bathe in.  Other compounds, like turpentine, evolved as poisons and should be treated as such.  However, I maintain that there is a real, if subtle, grey area between moderation and "cuckoo."  Unless we all start finishing exclusively with walnut oil, then we have to choose toxicity by degree.

-Ben