Enamel vs Urethane

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Model T Ford Forum: Forum 2009: Enamel vs Urethane
Top of pagePrevious messageNext messageBottom of page Link to this message  By Charles W. Little on Saturday, November 28, 2009 - 11:03 am:

I would like to get people's opinions on the pro and cons of acrylic enamel vs. acrylic urethane. From what I can find on the internet, the Dupont Centari that a lot of people like is enamel. " PPG" makes DAR-Delstar enamel and DCC-Concept urethane AND they make a "PPG Omni" MAE-enamal and "PPG Omni" MTK-urethane. Any one with experience with any of the PPG products? Also, there is a brand called "Restoration Shop" that has both an enamal and a urethane-anyone ever use this brand?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce Peterson on Saturday, November 28, 2009 - 01:26 pm:

Urethane is enamel that has a hardener component added. The more you pay for the products sold by Dupont or PPG the better the performance is regarding resistance to orange peel or any number of other potential problems in application. Also, the more you pay the better resistance to fading and cracking. Also, the more expensive paints are less likely to need as much work to achieve high gloss.

I've used all the products you mention. That being said I use Centari because it gives a decent finish for the money. Some of the other products are "too shiny" for a Model T, they give a show car finish that just looks inappropriate on a Model T.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck - Shreveport, LA on Saturday, November 28, 2009 - 01:35 pm:

"Urethane is enamel that has a hardener component added."

That isn't true Royce. You can add a hardener to Centari or other acrylic enamels like Omni MAE and they don't become urethanes.

Also, there are urethanes that do not use a hardener at all, such as spar urethane varnish which cures due to moisture in air.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joe Bell on Saturday, November 28, 2009 - 02:15 pm:

I personally like the Dupont Imron on the fenders and splash aprons and running boards for the climbing on and scratch resistance. I see the old boys carrying the old rug on a string and it is something else to clutter up the inside of a car with.I use the less expensive paints on the frame and body. You can sand and buff any paint to make them look like the hand rubbed lacquer finishes.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael F. Thomas on Saturday, November 28, 2009 - 07:43 pm:

I have never used Imron. I have always wanted to try it. I go back as far as Dulux. I used a lot of lacquer in the day. Went through lots of Centari with and without hardner. I really enjoy the new base and clear with hardener. Can anyone comment on how the Imron works in relation to all the previous mentioned? I would really like to try it on the next project. Is there a website from Dupont that will get a fellow up to speed on all their products? Thanks! Mike Thomas


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joe Bell on Saturday, November 28, 2009 - 07:58 pm:

Michael,
If you sprayed Centari, Imron goes on the same just wait a little longer between coats. I've used base coat, clear and like it real well but the clear tends to scuff a little easier than the single stage urethane.If the kids aren't going to climb on the car,I would say base clear.If you use the Imron have a fresh air respirator or supplied air, if not it will cause breathing problems later that eve.


Top of pagePrevious messageNext messageBottom of page Link to this message  By joe stearns on Saturday, November 28, 2009 - 10:05 pm:

Charles, I painted my Model T touring about 6 years ago with DuPont Acrylic Urethane and I'm very happy with it. It is Very durable and it is easy to fix a scratch with a little touch-up paint. My running boards are what amaze me--there are very few scratches where I step getting in and out. Good stuff but DO wear good breathing protection and cover ALL parts of your body for protection. Joefile


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob McDaniel (Indiana Trucks) on Saturday, November 28, 2009 - 11:19 pm:

Omni is less expensive than Concept but will oxidize outside in the sun where as I have had paint jobs sit in the sun 10 years and look like the day I shot them with the better PPG base/clear. Back then I used DBC base coat but it used a DRR reducer while the clear used a DT reducer. I think this caused problems between the two paints because the clear would come off after 10 years in the sun. If it sits inside 90% of the time it will last forever almost but the DCC I use now will take the same reducer in the base coat and clear (DT) and so far after almost 5 years on my truck it has held up 100%. I shoot at least 3 coats of clear and then wet sand with 1500 and buff it out and it will look like glass and stay that way. I have even shot this stuff on engine blocks and it holds up to heat!

The bad thing is the cost. If your car is perfect before you paint it use the best paint you can buy but if not perfect, fix the spots or use less expensive paint on it. You could still put single stage on it which is no clear and buff it out if you want and it will look just as good most of the time. Just remember, black will show everything!

Be safe if you use this stuff, it can do damage to you before you know it. You need air and good ventalation/exhaust fans. You also have about a 4 hour pot life after you mix the clear and you will use more clear than color.

Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By peter kable on Sunday, November 29, 2009 - 04:02 am:

I usually keep quiet in paint queries as the materials used in the USA are different to those here in Australia. For instance we have a Centari here but its not the same material as yours (ours is the European version) though it probably is still close to being the same quality.

My job for 40 years before retiring was to teach professional painters how to apply these paints in the Automotive, aircraft and industral industries.

Paint type is determined by the base resin which is used to make the paint. Its usually the clear component to which pigment and other products are added to make the coating. Every company makes several types of paint to supply industry ( and hobbists if they wish) that can be applied to surfaces.

In the automotive trade the paint needs to be able to match the qualities of the original paint. Something which didn't work real well when the only choise was Nitro Cellulose lacquer on the automotive and the equivalent to the oil base house paint which is still used widely.

An enamel is a high solid paint - this means it has lots of body and needs little thinning and dries glossy. Any time you see the word enamel you know that it dries slowly only requires about 2-3 coats and you should get a high gloss finish without the need to rub back and polish/buff.

Lacquer is the opposite it has a low solid content. meaning it has to be thinned with a lot of thinner (usually 100% or more) dries fast and needs lots of thin coats to build up the required thickness ( at least 5 thats why its outlawed now in California and elsewhere) and it will then need to be buffed to get the best gloss.
This takes time rubbing and buffing so the manufacturers set about finding a material that was a big step forward from what was available.

The answer was 2 part enamel it dried fast and hard because of the harderer dried glossy eliminating the rubbing and buffing steps but the penalty was IT WAS POISONOUS and and spray booths and masks became necessary.

The top of the line in these materials is Polyurethane enamel (Imron type) this is what is used on jet planes (Jumbo jets etc). it is meant to be sprayed on dry glossy and last years. You are not going to want to buff a jumbo jet or have to paint it often. Usually it lasts 10-20 years in conditions which are extreme. 500mph cold and then hot in hours rain dust etc. This is usually also sold as marine paint for the harsh conditions boats get being used.

Polyurethane dries rock hard and if you need to sand or buff it you need to do it soon after you apply it (within a week) or you will be working overtime to polish out scratches.

Motor vehicles need to be a little more forgiving. If there is a bit of dirt or a run or sag then it will probably need to be removed before the customer sees it on his belovered car. So a lesser material modified to allow polishing/buffing and spot repairing needed to be developed. Urethane enamels have these qualities. If they are good quality they are probably Acrylic Urethanes which stand up better in the Ultra violet of sunlight.

Depending on the brand and the support materials the painter uses it will provide a finish equal to or better than the original baked enamel finish from the factory. you should always use the recommended hardener and thinner for that paint for best results. You may find you also have a choise of products depending on what and where you live. (Hot/cold weather etc) The painter usually gets to choose the speed of drying in such conditions to control the final finish. He would probably use a fast drying hardener and solvent if the job was small but for a big job he might use a slower drying combination to allow him time to spray a large area.

What about base coat/clear coats? These were developed to get rid of the problems you can run into if the finish is not a normal straight colour (sorry color) metallics, pearls and other fancy finishes can be difficult to apply for the repairer but also for the factory. They tend to streak or become blotchy and they contain so much clear they don't cover over the primer well ( depending on the color of the paint and its primer) so they removed the large amount of clear . This made them cover well but they had no gloss so it was added as a separate coat over the top. Now the way they do this needs to be fast ( for the factory and the repairer) so the base color is a modified lacquer which can be applied and after a short air dry ( no baking) the clear can then be put on top and the whole lot dried.

Over the years this system has been vastly improved. The clears are so good now that even normal colors are applied as a base and cleared.
BUT the finish has in the middle a soft air dry coat ( should have a good 2 part primer under it) so it has a weakness which often leads to failure after time as the clear separates from the colour. So unless you have a silver or other fancy color its better to use a solid version of these paints. The black or whatever solid color you apply in the same finish will give the same result without the chance of it failing due to the sanwiched base coats. You will notice the difference especially if the paint gets stone chips the clear chips off the base a lot easier.

Always choose a finish that gives you the finish you desire, If you have spent lots of time and money rebuilding your T it would be stupid to pick a poor quality paint which won't last the distance. If you can apply a top line Urethane finish and do it properly ( with all the safety precautions) then go for it. Having said that I painted my Town Car with ordinary air dry enamel in red and black over 30 years ago ( before urethanes were available) and it still looks Good. Its kept in a garage when not being used and is polished regularly, if it lived outside all those years it would have packed it in after a few years.

Its been suggested that you use a hard finish on the running boards ( which you could easily paint outside with minimum safety gear or pay to have done professionly for a nominal cost) well worth it to get a hard scratch resistant finish. The body work could stand a cheaper finish and still give you years of service. Your choise but I'de always pick the best available for the little extra cost involved.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR. on Sunday, November 29, 2009 - 12:07 pm:

Peter -- I'm glad you didn't keep quiet this time. :-) Thanks for the "Painting 101" short course.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeff rey L. Vietzke on Sunday, November 29, 2009 - 12:54 pm:

I agree. Very informative and helpful. Thanks.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel Keefer on Sunday, November 29, 2009 - 02:12 pm:

Peter,
I also learned from your 101 course. Beautiful part was it was ALL in the same post.

Thanks,
Noel


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dick Lodge - St Louis MO on Sunday, November 29, 2009 - 02:28 pm:

Peter's post should be archived here somewhere...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Von Nordheim on Sunday, November 29, 2009 - 02:45 pm:

Peter,
Thank you for sharing your knowledge. Also, I have noticed clear coat turning slightly yellow over time. This is especially noticeable when applied over white or light base coat colors.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jon W. Griesenbeck on Sunday, November 29, 2009 - 05:09 pm:

I own a body shop and have been painting for over 35 years. email me with the results you want and I will steer you in the right direction. Remember no solid color has ultra -violet blockers in it. It is just in the clear. So if your car is going to be used alot remember that. I recommend Standox german paint Dupont bought it to get the technology. I believe it is the best paint on the market. It comes in straight color and base clear. It is a ureathane. All my cars are painted with it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By peter kable on Monday, November 30, 2009 - 06:27 am:

Thanks everyone for the comments,

Les, the reason clears go yellow is due to the effect of the ultra Violet light. It really stirs things up. makes the pigments fade and turns clears yellow. If you remember the cellulose in the windows of sports cars or cellulose sticky tape you will remember how it went yellow then eventually black and cracked. The yellowing is the start of that process.

You are right about the light colors and whites they obviously show a change as the yellowing alters the color and its easily seen. On other colors its not as obvious. On black etc it doesn't show at all, the clear has to go way past being yellow and start breaking down for you to see anything.

The worst paints for the clear to be involved with are as you state the light ones but also the metallic ones as the UV rays pass through the clear and are then reflected back up and out making the clear get a double dose.

Metallic paint has always had a lot shorter life on a motor vehicle. If you purchased such a color on a car you knew that it was going to need a respray within a few years probably half as quick as if you had a straight color. Lots of people made money respraying metallic colors because the cars became so shabby when they were still relatively new and low milage. It was necessary to repaint it just so you could get a reasonable trade in price when you updated.

Australia has real savage sunlight similar to Florida. Other places are a lot less severe. Queensland and Florida are the two major paint sites for companies to test the quality of their products against adverse sun and weather.

Some English cars used to have to be repainted here when new before they were sold up until the 1990's. Rolls Royces were all repainted with local paint as the original factory paint was so bad it failed before the 12 months warrenty was up so it was better to do it first so the customers didn't complain that their RR needed a repaint yet the local cheap cars didn't.

The clear component of paint determines how well it stands up to the UV. Nitro Cellulose (duco)was terrable, whites went yellow quickly and other colors faded and oxidized and needed polishing every few weeks. When Acrylic Lacquer came out ( I think "Lucite" was your name for it) it was based on "Perspex" (our name for the clear plastic they use still today to make clear headlight covers etc.)

This was such an inprovement they were able to paint cars all over in metallic colors something not really practical before though some cars which were baked enamel had such colors. Now it was possible to repair them with a material that would stand up as good or even better.

Now Acrylic lacquer is almost gone (especially in California) and the 2 part urethanes are the go. Still it wasn't till they found a UV inhibiter to filter out the UV's harmful rays that we have had really top quality clears that are available to use.

There is still poor versions of these paints so check with someone like Jon whose Standox/Dupont material is at the top of the list along with a couple of others.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charles W. Little on Tuesday, December 01, 2009 - 06:27 pm:

thanks to all for the responses and info


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ivan Warrington on Tuesday, December 01, 2009 - 08:20 pm:

I avoid Emron because it cracks. Why not use Lacquer? My all time favorite was Sherwin Williams Sunfire no longer available.


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