OPT said:
Supe,
Thank you for doing all this great testing and sharing your results and it looks like you did not need to dilute Opti-Coat for spray painting after all. However, I like to set the record straight about the solvents and solvency since I worked on formulating paint removers for a few years (I formulated the Aircraft Paint Remover used by most bodyshops) so I know a thing or two about solvents swelling paint to the point of delamination. Here is a list of the solvents in order of speed to swell and delaminate automotive paint:
Methylene chloride>>Methyl Ethyl Ketone (MEK)>Ethyl acetate (EA)>N-Methyl Pyrilidone (NMP)>propylene carbonate >Butyl Cellusolve (EB)>acetone
If you look up automotive paint removers you will find one or more of these listed on the MSDS.
"Some will "swell" the paint substrate, no doubt. Usually clorinated versions."
Ron,
Among these the only one that is chlorinated is methylene chloride. The rest are oxygenated solvents such as MEK or acetone. Lacquer thinner is a blend of MEK, EA, acetone, etc. These solvents can break the bonds of cross linked clear coat paint if left on the surface long enough. For instance, methylene chloride removes paint in about 10 minutes, while it takes 1-2 hours for MEK, and it requires hours or days for the rest of these solvents. Even wiping clear coat with these solvents in high concentration can cause cloudiness or hazing of clear coat.
"Oddly enough, two of the solvents mentioned in Ron's post were candidates that Dr. G gave me for thinning Opti-Coat. Time to find more thinning options..." Supe.
The two solvents I suggested to you at SEMA were xylene and paint thinner / mineral spirits (not lacquer thinner which is very different). However, I said paint thinner is too slow. While all solvents including IPA, Prepsol, xylene, paint thinner, etc. will swell paint, they will not cause any damage or break the bonds of cross-linked clear coat finish! These solvents have been tested and used for years and I think to just group them as "chlorinated versions" is not an accurate statement. Ron has a great deal of knowledge in automotive paint and bodyshop products and I am not sure if you have taken his quote out of context however over generalizing information can cause more harm than good.
Please let me know if I can be of further assistance. Thanks again.
David,
David.... THANK YOU!
That's exactly what I wanted to know. While spraying on Opti-Coat without reducing it is certainly possible, it would make the process much easier to reduce it first, hence the continuing investigation into ways to do this in a safe manner. I certainly didn't mean to question your expertise, but I was a bit befuddled as I had conflicting information from two highly respected and knowledgeable sources.
Shiny Lil Detlr said:
This is AWESOME! Thanks for the clarifications, David.
So if I'm understanding what you're saying correctly, as long as the solvent isn't going to dwell for a significant amount of time, there should be no cause for concern in using Xylene as a "reducer" in Opti-Coat to enhance flow-out of the coating during spray application.
My biggest remaining question then is whether or not it would be necessary to wipe the panel down after spraying to reduce the flash-off time of the additional solvent carrier (for sake of preserving a safety margin against paint swell); and for that matter I'm wondering if doing so would compromise bonding of the coating to the paint surface. Any thoughts?
:rockon:
Charlie, I don't think wiping down a xylene reduced layer of OC prior to the xylene flashing off would be a good idea...
From what I've observed, non-reduced OC "cures" in two stages: the very bottom part of the layer (that is actually in contact with the clear coat) latches on to the clear coat quite quickly; it cures faster than the portion of the layer that is not in contact with the clear coat. If the layer is too thick, the upper part of the layer doesn't cure as quickly... it's like the physical contact the bottom part of the layer has with the clear coat causes it to start to cure. After allowing the lower portion of the layer to adhere to the clear coat (around two minutes), it is safe to remove the upper layer; you won't remove the OC that has actually stuck to the clear. So essentially, you have a layer of OC that has two very seperate sub-layers: the layer that has bonded to the clear coat starts to bond almost immediately, then above that, you have a layer that isn't in contact with the clear, dries more slowly, and is easily removed with a gentle wipe of an MF.
One of the advantages of spraying on OC is that you're not constantly moving it around on the paint when it's trying to stick to the paint you're moving it across. Spraying it on, allowing it to stick, then removing the excess makes it much easier, IMO, to get a nice even layer than trying to herd it around the paint with an applicator.
Throwing a reducer in to the equation might change this a bit. The rate at which the lower portion of the layer attaches to the clear coat will, most likely, slow down due to the added xylene. So wiping down the fresh layer (like you would on non reduced OC) would probably become a bad idea; you'd be removing all of it. Of course, this is all speculation until it's actually tried, but I'm pretty sure this is what I'm gonna see happen.
There's two main reasons I'd like to reduce OC before spraying it:
1. Being able to see a wet layer makes it much easier to confirm proper coverage, and allows you to spray at higher pressures (smaller droplets) without the worry of "dry spraying" the OC.
2. Removing the need to do a post-spray wipe down to eliminate high spots of over application.
I bolded part of your post. In response, check out the part of Dr. G's post I bolded, too. Looks like we have our answer!
Can't wait to get to work on this. Unfortunately, temps have turned too cold for any more OC testing right now.
Dr. G, THANK YOU again for your help! (And if you ever want to produce a spray-ready version of Opti-Coat, count me in. I'll buy a ton of it!)
), those qualifiers "most" and "when used properly" can cover a lot of ground, or a lot of...uhm, backsides.
