Replies

1. 
   oldusty | Jul 16, 2007 07:28am | #1

        squarecut ,            

                We  create more VOCs by adding thinner to the materials , and that is partly why the specs tell you not to thin . Not because you can't get good results after thinning .

     Are you thinning at all ?

       Not spraying outside ,,,   not spraying during the hottest parts of the day ?

            I won't use the retarder any more , the spray dries too fast in the extreme heat and produces a rough finish so after about 80° I may shoot sealer but not the top coats . Start at 6am and be done spraying by lunch .

        When I used a conventional cup gun I thinned about 40% more or less . I applied several thin coats that for the most part laid out and flowed .It seems I shot at about 40psi .

     I shoot with an Airless pump now and usually still thin close to 20% sealer and top coat . Many of the lacquers are now self sealing where you can,use the same product on all the coats , no sealer no thinning is what the manufacturer's are suggesting , it certainly can be done but the average occasional finisher may take some practice shooting straight lacquer , by golly !

                              regards     dusty

1. 
   squarecut | Jul 16, 2007 03:39pm | #2

   Thanks, oldusty!
   Sounds like the heat is my biggest problem but thought the retarder would help. Guess I'll get up earlier too.

2. 
   Hastings | Jul 16, 2007 04:05pm | #3

   Square:

   I had a similar problem when I started spraying. There are a number of posts going back several years that you might also find useful (I did). Just search under "spraying" and "Lacquer"

   Kevin, who frequents Knots is a real expert. Here was his advice to me after encountering problems:
   QUOTE:
   For what psi to spray it at... I would suggest that you simply use the least amount of air pressure that gives you a decent spray. There are so many variables that I'm hesitant to suggest a specific psi and besides, my gravity guns all have cheater valves built in and I adjust my air pressure there, so I don't know exactly what psi I usually spray at. I'd guess that it's somewhere around 15 to 20 psi.

   As you may have gathered from some of my older posts at Knots, I am very fond of reducing lacquer with a blend of Methyl Ethyl Ketone and PM Acetate rather than with a prepackaged lacquer thinner. PM Acetate is the retarder that I like best. But retarding too much can make runs or sags in the lacquer a real issue to be concerned about. That's why I like to blend the two solvents. MEK flashes pretty fast and that helps the lacquer to hang rather than run or sag. It's not a cure-all, but it does help.

   For spraying out of a gravity gun I would thin the lacquer approximately 10 to 20% with the above mixture. A baseline mixture would be 50% MEK and 50% PM Acetate. But I'd adjust that to meet ambient conditions. In cooler weather you'll want a higher percentage of MEK, in warmer weather you'll want a higher percentage of PM Acetate. Although I think you'll find that the 50/50 blend is very versatile.

   Another trick that should help would be to do what I call a "Painter's Two-Step." Basically what I do is to split the finish coat into two steps, which allows me to get a good build while minizing both overspray and runs/sags. For the first coat I put it on not quite fully wet. What you want is about 80-90% flow out (wetting) so that it's almost fully flowed out but not quite. Give it a minute or two to flash off and then come right back and lay it on heavy enough to get full wetting. What happens is that the first coat's solvents partially flash off leaving room for the excess solvents in the second coat to soak into. The net effect is that the two coats become one but with a lower total solvent amount... which is much less likely to sag or run, but sprayed close enough together as well as the second coat being heavy enough to eliminate overspray and orange peel. It will take some practice. But once you get used to it you will love it.

   You say that you are doing a cabinet. Are you finishing both the inside and the outside? Enclosed spaces are difficult to spray and it can be very difficult to avoid overspray, particularly in warm weather." END QUOTE

   I am now getting pretty good results, but it has taken time and practice (what doesn't!). I am spraying outside in high heat, high humidity (Gulf Coast). I always spray in the morning because of afternoon storms.

   Last week, I cut back on the retarder and started seeing some blush so I left it 3% and it is fine.

   I showed some work to a professional (high-end boats), who thought the finish, after rubbing out, was excellent.

   I was very discouraged for a bit, but now I enjoy the spraying!

   Regards,

   Hastings

3. 
   mudman | Jul 17, 2007 08:14am | #4

   Your gun settings wont change the flash off and "dry fall" issues you are having. Here in Texas I regularly spray in 100 degree heat with a 4 stage turbine system that blows air as hot as a hair dryer! I use copious amounts of thinner and retarder. Thinner is what will get the finish to spray wet. Try adding 30% thinner, increase untill is sprays wet with no dry fall (dry fall is that dusty dried-in-the-air stuff at the edges of your spray pattern). Then add retarder untill it flows out nicely. On a 90 degree day I might add 30% thinner and 15% retarder. On my final coat I increase the retarder to 25 or 30% for a perfect surface. Thats right I might only have 40% Lacquer in the cup!

   It sucks to use so much VOCs but what can you do? Lacquer used to flow out a lot better but they make us add all the thinner/retarder now so the product will meet federal standards. The expensive stuff works better out of the can, but Sherman Williams will give the same results once you learn to mix it to suit you.

   As far as your gun goes the best advice I can give is to keep the gun close to the work. 6 to 8 inches is good. When I was learning I would tend to pull the gun away to keep the finish from building too fast, you need to keep the gun close and move fast enough that there are no runs, but slow enough that the finish goes on wet. The actual settings are too arbitrary to really recomend. Some guns (HVLP) use 20 Psi at the hose and some use a lot more. Some guys like to keep a tight pattern that builds quick with less overspray and others like a wide pattern that requires a slower hand but makes more dry fall. Every gun and person are different and after a lot of messing around you will learn what works for you. The mixing of the finish is a little more concrete, but even there I know a lot of shops that dont try for the same quality of surface and are OK with a little orange peel.

   Pardon my spelling,

   Mike

   Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.

1. 
   squarecut | Jul 21, 2007 01:56am | #5

   Thanks for the info!

4. 
   Kevin | Jul 21, 2007 09:43pm | #6

   You got some good advice here. Hastings saved me the trouble of posting a long, detailed list of suggestions, but I'd like to briefly cherry-pick some of the key points in the responses you've received thus far.

   OldDusty's advice about not spraying finish coats during the heat of the day is hugely important and simply can't be overstated or overstressed. I disagree with him about not using retarders. But even using retarders I would still strongly encourage anyone to avoid spraying topcoats above 85 degrees or so unless they have no choice AND are experienced and competent at dealing with the heat issues via retarders and spray techniques. And even there I would say that it's sheer folly to attempt spraying even sealer coats above 90 - 95 degrees. Whatever time one thinks he/she is saving by squeezing in another step that day will usually cost them more over the following day or two trying to fix problems that occurred spraying in such high heat conditions. Believe me, I've seen it happen!

   Mike's (mudman) advice about spraying close to the surface resonated with me when I read it. You'll find that all of the formal spraying books and such advise against spraying too close... and for very good reasons. But once you've become competent at spraying and no longer need to refer to such suggestions you'll... or at I'VE found that I prefer spraying a wee bit closer than the formal suggestions say is ideal. The reason is that I can cover more ground, faster. But the key to making it work is that you have to spray faster too. It's a bit dicier and you really have to be on your "A" game in terms of focusing fully on what you are doing and knowing how to proper cope with all of the other details inherent in spraying lacquer, but you'll also have more control in some ways than if you sprayed at a greater distance from the surface.

   You may or may not come to prefer spraying close to the surface. But if you try it just remember that you have to also move your arm faster comensurate to how much closer you are to the surface.

   Lastly, "retarder" is a vague term. Not all retarders are equal, mostly because there's a variety of different solvents that will retard the drying of lacquer. So make 100% sure that if you follow someone's suggestion of a given percentage of retarder added that you are using the same retarder. 20% of Butyl Cellusolve and 20% of PM Acetate are going to produce PROFOUNDLY DIFFERENT results. Butyl Cellusolve is an extremely powerful retarder, whereas PM Acetate is a relatively mild retarder. Adding 20% of the former is a disaster waiting to happen, while adding 20% of the later is going to be difficult but workable under really mildly hot weather.

1. 
   oldusty | Jul 22, 2007 06:29am | #7

      Hi Kevin ,

                   As far as retarder goes , not sure what you don't agree with ? I only said , I no longer use it . I have used it and gotten good results in the past .

        What I have noticed is when the temp and atmosphere get to the point that the spray dries too fast instead of using retarder I simply stop spraying top coats . As you said after 85 degrees or so with or without retarder , spraying gets dicey .Also perhaps the airless produces better results even at warmer temps then conventional rigs .I suppose it has to do with the way the guns atomize the materials and the fact that no air only material is being sprayed . So for me I have eliminated the need for using retarder and I typically get excellent results , after 35 years of practice it becomes second nature .

        The worst time for me to spray is about 55° and raining , the humidity causes blush .

    Imho the use of MEK or other even more volatile chemicals is simply not needed and can be more hazardous then the Lacquer and thinner can be besides for some diy types it could be considered risky , care needs to be used when these strong chemicals are used . 

                           dusty

1. 
   Kevin | Jul 22, 2007 06:55pm | #8

   Ah, I think I misunderstood the point you were making. It makes perfect sense that an airless rig would pose less of a need for retarding solvents because it mechanically atomizes the fluid stream rather than using air to atomize it. It's been many years since I sprayed with an airless system, and even quite a few years since I've sprayed with it's close cousin the air-assisted airless. The commercial airless that I first learned how to spray with further negated the need for added solvents by heating the lacquer to reduce viscosity rather than using thinners to accomplish the same task. However the furniture factory which used it still used retarders in hot weather. It's a great way to go with several distinct advantages over conventional systems, but well outside the means of most DIYers or even small companies.

   The thing that I like about MEK other than it's fast flash and high solvency is that it reduces the surface tension of the lacquer particles which helps them flatten out more quickly/thoroughly when they hit the surface being sprayed, thus working to negate orange peel and overspray to an amazing degree.

   I do agree with your caution regarding the hazardous nature of the more volatile materials. However it seems to me that if an individual is taking the proper precautions (respirator, nitrile disposable gloves [which I always wear], etc) then they are no more hazardous than the lacquer itself. Frankly, if a person is avoiding hot solvents but not taking good personal safety precautions then they are taking a significantly higher risk than using the hot solvents while taking proper safety precautions.