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Old 02-03-2011, 10:26 PM
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Confused about modern paints and lacquer - softer or harder

Hello to all,

After searching many internet sites I am confused about the modern paints. 50% of sites claim that lacquer is softer and the old compounding products used for Lacquer can't cut the urethanes, others claim that lacquer is a harder paint and that is why it chips off. I have personally seen very hard lacquer crack. What is the real answer, I'd really love to know out of interest.



The old books I have for lacquer sanding/cutting/polishing tell me to use

1: color sand with p1200
1: lambswool with cutting compound at 2400 rpm
2: dry buff at high speed with clean lambswool
3: dry buff again at high speed with cornstarch to remove swirls.


The book explains that urethanes need special compounds and buffing pads or they will get a haze instead of a shine.

Why exactly is this, do urethanes smear because they are softer or is it that the older compounding stuff uses a softer polishing grit???
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Old 02-04-2011, 12:59 AM
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What you learned yesterday may not apply tomorrow. I don't know that there is a general answer to your question, but Shine, Barryk, a few of the others will be able to splain it all better than myself. Give them a few hours to sleep.
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Old 02-04-2011, 05:56 AM
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Well you cannot make a blank statement about any of this.

Yes, lacquer is hard but all lacquers back in the day varied as far as hardness.
Nitrocellulose was softer then any, PPG was softer then Dupont (25 years ago)

If for example, you use a 2 pencil hardness with lacquer and a urethane clear, the urethane would still be way more stone chip resistant and way stronger, because of the natural mil build up and the ISO used, the same forced build with a lacquer would weaken it.

Cracking in the lacquer is not related to the hardiness as that is a result the the lacquer losing its solvents with age just like a plastic piece inside your car when it cracks.
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Old 02-04-2011, 06:30 AM
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Quote:
Originally Posted by BarryK
Yes, lacquer is hard but all lacquers back in the day varied as far as hardness.
Nitrocellulose was softer then any, PPG was softer then Dupont (25 years ago)
.
How about today's modern lacquers? the ones that are 2k?..
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Old 02-04-2011, 07:02 AM
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I'm sorry, forgot about different slang for different countries.

Yes catalyzed lacquer is AKA urethane or enamel depends on brand.
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Old 02-04-2011, 07:51 AM
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Quote:
Originally Posted by BarryK
I'm sorry, forgot about different slang for different countries.

Yes catalyzed lacquer is AKA urethane or enamel depends on brand.
No.... I mean Real lacquers that are catalyzed like permalac..(which its not a automotive but industrial coating)

BarryK I once did mixed a Urethane Universal catalyzer with good Old Lacquer(nicaraguan brand) and it worked just fine...
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Old 02-04-2011, 08:25 AM
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Sorry don't know what permalac is but if it has enough polyol to take a 4:1 mix or more of ISO, it enamel or urethane.

I think it is just a confusion of language barrier as the Germans still call urethanes catalyzed lacquer and really technically it is.
When they first made appliance paint it was called catalyzed lacquer before being called enamel.

Anyways, just splitting hairs.
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Old 02-04-2011, 08:39 AM
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Quote:
Originally Posted by BarryK
Sorry don't know what permalac is

Anyways, just splitting hairs.
Permalac uses a 2:2 mix
http://www.permalac.com/Products.asp

Thanks anyways...
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Old 02-04-2011, 09:08 AM
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I'm an old lacquer guy who used it for over 30 years. Lots of disadvantages compared to the new base/clear uros. Either one will take a while to get familiar with it.

For urethanes, the sandpaper grit will vary with the brand. 1200 will work for those that stay soft longer. I use it with my R-M DC92 Diamont Clear. For the clears that set faster... some get so hard that you will double the manhours to finish them, so guys "finish sand", sometimes using three different grits up to 2500, before they even start buffing!

Very very few use lambwool pads today. Same problems as the old days. Major buff marks and you can build too much heat! I use a stiff "gray" foam waffle pad and 3-M 6031 compound, then finish with a "white" soft waffle pad and 3-M 05973.

Using my clear and buff materials, I have several days to sand and buff before it starts to get a little harder to work. I've used it for about 5-7 years now with zero complaints... minimal working time... and very long-lasting gloss.

You will find that each painter has his own preferrence, but I have used about six different urethane clears and like this one best for ease of use, adaptability to shop conditions, and for final finish.

Last edited by TucsonJay; 02-04-2011 at 09:15 AM.
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Old 02-04-2011, 01:37 PM
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I spent many years calling on paint companies here in the US selling raw materials to build paint. Lacquers are a thermo plastics, they will try to go back to liquid if heated up. This is why they burn when over buffed, it heats up and starts to move on the pad. there are catalyzed lacquers, but at least here the US, they are only used on Kitchen Cabinets. Catalyzed systems like base coat clear coat are higher in viscosity (thicker) than lacquers and higher in total solids (what is left after the solvent is gone). Either coating with clear will weather better than with out clear. Problem with lacquer is that is has a plasticizers in it to make it flexible. This is really just a very slow solvent that leaves the film in time. Then it becomes brittle and cracks when hit. The harder a coating is, the more it can and will crack. Testing run on coatings tests them up to 160 inch pounds of force, most will crack at that level. But softer coats will perform better than very hard ones. There are flex additives that are used in base coat clear coats over plastic bumpers since they flex more than the steel body. These are also tested with a rock throwing machine to check chipping. Again shows up more when panels are cold. Tests are run on very cold panels as well as hot to make sure coating will work in winter as well as rest of year.
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Old 02-04-2011, 03:08 PM
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lacquer

Nitrocellulos lacquer was used before world war 2 on cars, planes, bikes,etc. etc. It dried very slow between coats! It used to be rubbed out with bakeing soda and gasoline [Hand rubbed]. During world war 2 the war effort needed fast drying paint it was still nitrocellulos but mixed with fast evaperating agents [and thinned again with good old lacquer thinner] this was used well into the 60s and some 70s like ppg glamour color! It would chip,some brands would yellow, some brands would crack with age[NOT ALL]you got what you paid for back then too!!!! The new acrylic laquers replaced the old nitrocellulose. The new acrylic lacquers do not yellow are more durable and stable over time!! But again you get what you pay for!! one big mistake is useing example METALFLAKE BRAND or HOUSE OF COLOR and off brand thinners or just buying cheep paint. PPG is very good I use it a lot when my customers will pay for it!!! I still use nitrocellulose when my customers insist I did a docters buggy a few years ago[horse drawn].hard to get!!! I use the acrylic lacquers a lot, you can repair it 30 mins. after shot, you can add layer on layer like 30 coats , and I still hand rub but not with gas!!
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Old 02-04-2011, 03:17 PM
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about the gas

Please dont even think about using GAS!!!!! If any one even considers it its crazy !!!!They did this years ago different time different era!!!! Different paint! DIFFERENT GAS!!!!!

Last edited by painted jester; 02-04-2011 at 03:23 PM. Reason: addon
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