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  #16 (permalink)  
Old 03-13-2005, 04:47 PM
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Barry,
Very cool info here!!!
You say that some clears will turn milky and others benefit from clearing,sanding and more clear.
Any tips or general rules to know which ones work and which ones dont?...Eric

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  #17 (permalink)  
Old 03-13-2005, 05:18 PM
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Quote:
Originally Posted by sevt_chevelle
Barry,
Very cool info here!!!
You say that some clears will turn milky and others benefit from clearing,sanding and more clear.
Any tips or general rules to know which ones work and which ones dont?...Eric
**********************************************
The premium ones but a little common sense also. Example what is real popular at a dealership for Dupont, 7600, 7500, 4700 so they won't work, now 7800 very expensive and not usable in a dealership, so most likely a good choice. This is the best I can do here without getting myself in trouble.

Best clears will always be 3:1, 2:1, 1:1 mix a 4:1 will always be a lower grade. These mixes don't guarantee they are the best, it just depends what there made for and why.
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Old 03-13-2005, 08:41 PM
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Very interesting stuff, I recently witnessed the milky clear phenomenon myself. Did a few jobs with Lesinol Universal clear and noticed if I did the clear sand clear thing I actually lost depth! The shine off the surface was fine but clarity was bad. Two coats of the stuff looked fine and after that it went south. On the last one I let the basecoat flash quite awhile thinking that is may be solvent being trapped, but no luck. A good friend of mine is pushing the Lesinol so I gave it a try, PPG global D893, D894 rank at the top of my list for clarity. Dupont's 7900 sure looks nice from what I've seen but I haven't tried it myself.

Another interesting thing about doing the two step clear vs. applying three or so and doing the cut and buff is I see much better durability doing two clears. I think because usually less material needs to cut from the surface before buffing. Is there important components in the clear that float to the surface that sometimes get removed if major sanding is done?
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Old 03-13-2005, 11:47 PM
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By they by, I did a test once to clear up the myth that you needed a lot more clear when you cut and buffed because of all the material you would remove. Well, .5 mil is all I removed with a thoroughly flat cut and buff.

Yeah Barry,what about Bobs question on the top "layer" of clear being needed?
Brian
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Old 03-14-2005, 05:13 AM
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Is there important components in the clear that float to the surface that sometimes get removed if major sanding is done?[/QUOTE]
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

Your UV protectors can.
But with wetsanding and reclearing this is not a concern or an issue, because the UV inhibitors in the first clear is cured and they are stable.
What happens in clear the the UV inhibitors form a chain (molecules) and the weight of them in the clear causes them to settle toward the bottom of the clear as the clear cures.. Parts of the chain break off and individual molecules float to the top as free radicals. Its these free radicals that are the problem if you wetsand say a month later than within the first week as you can sand them out and you lose some of your UV protection.

Now in real good clears, there is a second UV additive you can use, its part of the HALS group of chemicals and what this will do is mate-up with the free radicals and by doing this will drop them deeper in the clear during the curing process, so now wet sanding six months later will not effect the clear.
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Old 03-14-2005, 06:37 AM
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Barry, You are one knowledgeable paint guru, thanks for enlightening us on the clear. One more question if you don't mind, have you done any testing related to baking vs. airdry and if durability increases? I've heard yes and no on this from so many people over the years. My guess is that the baking only speeds the cure process with no affect on durability? Bob
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Old 03-14-2005, 08:20 AM
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Wel, I guess we now have some "clarity" on clears . Something I've always done on show work was to surface my base to alleviate the dreaded "urethane peel" syndrome. Even though basecoat dries flat it's still there in the final product. Maybe not at the "in your face" distance of the person doing it, but from any distance of 20+ feet very apparent. Seems to me that what you've done follows the same pattern of thinking albeit later in the game. Someone above mentioned the lacquer days. Looking for flat. From the metal to the clear and all steps between makes for flat, which then makes for clarity. My weapon of choice for surfacing the final clear is a paint stick wrapped in 1500, then 2000, then 2000 on a Meguires pad to "polish" the surface, and at that point very little wheel time is needed. I never really cared for the look of re-clear vs surfaced. I'm kinda with Martinsr on that one. The info posted though gives lots of input to "getting there" in many ways. And I fully agree about the clear content/quality thing. I get a seriously deeper finish with HOK vs PPG. The last great PPG product IMO was DAU 82 clear. With that I could actually outdo some of the best lacquer efforts, at ANY distance.

Thanx for a great post Barry.
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Old 03-14-2005, 01:50 PM
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One more question if you don't mind, have you done any testing related to baking vs. airdry and if durability increases? I've heard yes and no on this from so many people over the years. My guess is that the baking only speeds the cure process with no affect on durability? Bob[/QUOTE]

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

I'm only speaking for Acrylic urethane and polyurethanes, don't know about enamel or lacquers or latex paints.

You are right in your statement, it only acts as an accelerator but whatever pencil hardness the clear is set to be say a 2, it is not going to change that one bit.
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Old 03-14-2005, 02:15 PM
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As a guy that shouldn't even be allowed to play with a crayon, I have a few thoughts in regards to the reflectivity of the clears.

1.) Would cutting with the 320 require more time with the buffer, to "burnish" the clear more? (Stands to reason, that it would)

2.) What would the results be if each panel were buffed the same amount of time regardless of the grit?

I wonder if the additional time with the buffer is heating the coating enough to polish to a higher sheen, or if the 320 levels it better than the 1200.
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Old 03-14-2005, 03:40 PM
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Hi guys, I was just surfin the net and came across this site. Ive been a professional painter for the last 26 years. As far as clears go,only small under equiped shops use anykind of proformance clears and only for jamming or spot repairing panels. Most use one clear with differant hardners and reducers to regulate the dring times. Most of the best paint companies are european ,Sikkens,Glasurit, Spies Hekker ect. Dupont is probablly the worst. The only reason anyone sands and reclears is to eliminate orange peel. The best gloss will always be right after spraying.Once you sand and buff you lose some gloss but gain a better overall look,Slicker,cleaner.


Hope this helps
Craig
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Old 03-14-2005, 03:55 PM
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The 320 is the color sand between coating,not before buffing.
You'd have to REALLY work it over to get rid of a 320 scratch.
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Old 03-14-2005, 04:04 PM
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320 is way to agressive, your just taking off all that expensive clear. 600 wet should be the most ever used on fresh paint.
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Old 03-14-2005, 08:47 PM
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Quote:The only reason anyone sands and reclears is to eliminate orange peel. The best gloss will always be right after spraying.Once you sand and buff you lose some gloss but gain a better overall look,Slicker,cleaner.

Sorry p8nter but I beg to differ with ya. The amount of gloss has a direct relation with surface texture which can be perfected with sanding and buffing not obtainable by just spray application. Sanding and reclearing makes sense when more than 3 coats of clear are being applied. By spraying three coats of clear and sanding then reclearing gives the clear a better cure and also controls shape and texture. Have you ever thrown 5-6 coats of clear on a car without sanding between and seen all the edges build up and dieback from all of the buildup? More clear adds more depth, more depth adds more eye candy. If you sand and buff correctly there will be no loss of gloss only a noticable impovement! In twenty years I have not seen any as sprayed job that could not be improved with colorsanding and buffing. What makes Dupont the worst in your opinion? I've used some european products that weren't very impressive IMO.
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  #29 (permalink)  
Old 03-14-2005, 09:00 PM
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Is it even POSSIABLE to spray a "perfect" last coat of clear?

Not in MY neighborhood anyway,

Paint it, and THEY will come... &#$@!%#$@##$#@
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Old 03-14-2005, 09:38 PM
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Have you ever thrown 5-6 coats of clear on a car without sanding between and seen all the edges build up and dieback from all of the buildup?

Sorry no, Ive never had too. 5-6 coats is way to much and is the cause of most
paint problems other than poor prep work.With these new high solid clears
three coats is max, Most are two coats and still have some buffing room. Putting that much clear on traps solvents, causes fish eyes and peeling problems.
You are talking about basecoat /clear coat urethane right and not lacquer.
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