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Experienced vs rookies
In my books, I always recommend to stay with one paint system throughout any particular project, whether it is PPG, Dupont, or whatever. This is simply meant to avoid any incompatibility issues. There are all sorts of "stuff happens" issues that can wreak havoc with a paint job, that you don't need to test fate any more than necessary.
Can you get acceptable results by mixing and matching components from various systems? Probably, but do you want to take that chance? I sure don't want to sand it all off again if it doesn't turn out right. If you are an experienced painter, you can probably figure out how to correct most problems, but a rookie probably would not be able to save a botched paint job. Just my two cents worth. By the way, How to Paint Your Car, 2nd Edition should be out next spring from MBI. Dennis W. Parks Author of Automotive how-to books |
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Well in all actuallity I never do repaints over factory paint, I don't do collision work. They are always to bare metal then an overall repaint over fresh substrates. It is restoration work, period. Not the same as what your talking about.
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A sealer isn't any more "compatible" with the old paint than anything else, in fact it is thinner to lay out better so being it has more solvent in it it is more likely to lift something or fail in some way.
Sealer is used for a number of different reasons. 1. Poor prep, too course of sanding for instance. 2. Make a uniform color for easier coverage with your paint. 3. Small sand thrus. Brian |
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don't forget bleed thru. If you block on an existing paint and you had to go thru a layer or two a sealer is great at keeping things separated as to not create halos or rings or an edge sucking up the shine. If it does lift I'd rather be sanding on that and reseal lightly than trying to do it with base. Sealer is great insurance for a number of things
Last edited by tech69; 12-27-2012 at 07:57 PM. |
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no one would chance not use'n a sealer coat.. and that paint can be 20 years old.. it's as cured as it'll ever be |
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take my 86 SS 8700 miles.. never titled till 2001 never hit, never anything other than the paint is 26 y/o and tired from lack of care.. it doesn't NEED or warrant a down to metal repaint.. as the paint is tired from the showroom rub down it got way tomany times.. that killed the paint.. not many are dumping 10k on a paint job on a 1500.oo -10k car.. and there are tons of these in the hobby. no matter if YOU don't do them |
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The original question, should a painter stick with one product line through out a paint job. The simple answer is, in an ideal world , yes. If the question was can I use one manufacturer's product over another, or is it safe to use one manufacturer's product over another it gets a little more complicated...and...Brian, your right. The key word is cured.
If your using a PPG primer that is catalyzed and you want to use Dupont base, with SPI clear and if your asking if it will work safely, I would say Yes...under conditions. If the PPG primer is cured and I mean cured and prepped properly you can safely put Dupont base over top...the Dupont base, when totally flashed will accept SPI clear. This is no different than painting over top OEM finishes or over some other shops previous repair....If it wasn't safe, it would be mandatory for shops to out line what products they put on your vehicle when it was repaired or for the manufacturer to tell you which product line your vehicle was originally painted with...Example...For several years now the OEM has been using water born base coats and shops are repairing them with solvent base coats...they still get successfully repaired. Then we get to sealers....I have posted several times what my feelings are about sealers...but...here goes again. Sealers, in my opinion, are not a necessary step. If they where, a color blend would not be recommended by paint manufacturers. If you know what your substrate is and that your substrate is consistent throughout your panel that you are painting and your substrate is prepped properly, sealer is not required and is just another coat that you can get dirt in. Sealer is an excellent product if your prep work is questionable, for example, if the manufacturer recommends that your substrate be prepped in 400 grit paper and the substrate is prepped in 320..a sealer will fill the 320 grit profile and eliminate sand scratches in your top coat. If your substrate is questionable...you don't know if part of it's lacquer, part acrylic enamel or base coat, sealer may offer you a "sandwhich" degree of insurance knowing that all of your paint is going over top of the same substrate...but...you don't know how the sealer is going to react with all of the different substrates underneath it. The difference is substrates underneath the sealer will contract and expand differently, absorb solvents and catalyst differently and could still cause "halos" or even wrinkling (if the sealer is shot over a non catalyzed product like lacquer or enamel or if the existing substrate has been oxidized to the point that it hasn't any properties of a freshly catalyzed product). The key answer here is know your substrate, if your unsure, test it by pepping the substrate, wiping it clean with a thinner, if your rag with thinner ends up being the same color as the substrate your wiping...chances are you have a weak substrate and it should be removed....if your still not sure, spray some sealer, primer, base or whatever over the prepped substrate, if it reacts by wrinkling, extra long flash or cure times you have a weak substrate and it should be removed. If your still unsure, because of it's age, fading or you just don't get a good feeling, remove it, if you don't, chances are your going to in the long run and having double the material bill. The days are long over of dusting lacquer primer over top of poor substrates to build a weak bridge before painting...if there not over...they should be...that's just a poor repair or method of trying to get to a respectable finish. Hope this helps Ray |
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If that's what you want...your call...there's nothing wrong with that, as I mentioned, there are many places and people that would do that, I wouldn't, it's my name and reputation that I'd be worried about. If I painted a car like that and something happened....The first question would be, who painted that car??? Not, didn't you want that car stripped? or, Why didn't you get it done properly in the first place? It always lands on the guys lap that agreed to do it for cheap...If I do it right, and something goes wrong, at least I would know what I was working with be able to fix it easier, knowing what's underneath. Ray |
| The Following User Says Thank You to 69 widetrack For This Useful Post: | ||
cyclopsblown34 (12-28-2012) | ||
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Thanks Ray |
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if it's a laquer paint on a all original car, I'd go to metal.. cause if it hasn't spiderwebed(checked) it will... got to remember mid 80's and newer are 26+ years old now.. tons of these are getting rodded, as most don't have the green for the 64-72 cars,, or s 32-34 ford.. 55-57 etc.. myc-10(71) will go to metal, as the new paint buy the p/o (2000) lifted the oem paint, but not the primer under it.. no idea what gm used on trucks in 71 (enamel??) but the mid line duport pulled it up.. 30 years later.. if it was the new paint only lifting, I'd say p/o prep was the cause.. but it pulled the factory paint.. no sealer was used as far as I can tell.. from a d/a and feathering a spot |
| The Following User Says Thank You to gearheadslife For This Useful Post: | ||
tech69 (12-28-2012) | ||
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[QUOTE=gearheadslife;1627930]most times the baked on paint from the factory is a better base than going to metal and starting over.. depends on the car..
if it's a laquer paint on a all original car, I'd go to metal.. cause if it hasn't spiderwebed(checked) it will... got to remember mid 80's and newer are 26+ years old now.. tons of these are getting rodded, as most don't have the green for the 64-72 cars,, or s 32-34 ford.. 55-57 etc.. myc-10(71) will go to metal, as the new paint buy the p/o (2000) lifted the oem paint, but not the primer under it.. no idea what gm used on trucks in 71 (enamel??) but the mid line duport pulled it up.. 30 years later.. if it was the new paint only lifting, I'd say p/o prep was the cause.. but it pulled the factory paint.. no sealer was used as far as I can tell.. from a d/a and feathering a spot[/QUOT Factory paint is baked on...this is done to keep the assembly line moving...Body Shops that have an air make up unit with their booth also bake their paint to keep the production moving. Baking paint doesn't make paint better...paint will cure over time and be as strong as unbaked paint. I'm sorry, I'd like to respond to the rest of your post but, maybe it's the fact that I don't understand all acronyms, I'm not sure but, I am having trouble understanding what you are trying to say. If you could help me out with what "p/o prep" means....does the p/o stand for pour overall? |
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