SPRAYING REAL URETHANES

[E St. Kruiser50]

This is more of a topic and coversation starter than a tutorial.

I've read enough posts here on the subject to know there are different opinions, like most everything we talk about here, so if what I do differs from anyone else, it's just about how I do it, and hopefully it may help others, and maybe someone will have suggestions and help for me get better too . Remember, this is not a dissagreement with anyone elses techniques or choice of materials to use.

Most of my builds I like to use rattle-can lacquers like Tamiya, dupliColor and plastiCote.

I hear Testors lacquers are good too, but haven't used them.

But for my high-end stuff with a lot of work in them, I usually choose urethane, because of the extra depth and brillance I get.

I sprayed my first catalyzed urethane paint job back in around 1974 or '75, on my 1 to 1 '57 Pontiac Safari Wagon I had resto-rodded.

On model cars I've been spraying urethanes about 10 years.

I took the plunge right off using HOK candies, pearls and metalflake. I used their reducers, catalyst, SG 100 inter-coat clear, and the UC 35 clear that get's catalyzed with KU 150.

The other brands like Dupont and PPG are pretty much the same, and work well also. I just like HOK's selection, quality, availability, and the over-all way they have created a huge compatible paint system that works so well.

Also, a nearby auto paint store specializes in all the HOK paints and supplies that are available.

They also carry the two different urethane primers I use as a base.

There are different opinions about what to use, like using lacquer thinner instead of reducer, which I don't recommend and neither does the manufacturer.

For me I have too much time and money invested in a build to take a short-cut on the last stage of a build, and take a chance of ruining it for the sake of a few dollars.

When it comes to painting I do everything by the book, and the manufacturers recommendations, and it's never let me down.

So that's what I recommend to everyone else.

WHY PAINT WITH URETHANE AUTO PAINTS??

When it's done right on a model car, it'll always give you the best finish IMHO, and stand out at any event.

Under the scrutiny of car show lighting, swirl marks always show up in any other type of paint - lacquers or enamels- it's the nature of the paints.

Urethanes on the other hand are a different breed of animal, and finished properly, have no swirl marks under any type of lighting.

Also, the depth and brillance of urethanes has no match by any other paint IMHO.

When I take a model to an event, be it model club meeting or contest, one of the first things commented on is the "Brillance" of the paint, and the high lustre of the finish, when finished in urethane.

That's not about me, but about the effect of the materials used.

DRAW-BACKS

There are sevaral draw backs to using urethanes.

COST , when done right with quality materials, cost can be excessive for some.

SKILL LEVEL - If you aren't an accomplished painter with other types of paints, like lacquers, you may find urethanes to be way over your head, and may be a goal to use sometime down the road when you have more successful experience.

LABOR INTENSIVE - Compared to lacquers, whether rattle-canned or air-brushed, urethane is intense.

Each coat has a "window" of 16 to 24 hours for re-coat and finishing, with 15 minutes recommended between each coat according to the manufacturers.

Once you're in it , you stay there until your done.

The RETRO-VETTE took me 4 to 5 hours to paint, with all the different paints mixed ahead of time. The white base color, the yellow, the natural pearl mixed into the SG100, and then lastly the catalyzed clear.

3 coats of each of the colors, and then 6 coats of the clear.

15 coats of paint sprayed 15 minutes apart, plus spray time, and that doesn't count the urethane primer used before hand for prep.

Add 4 to 5 more hours for prep work.

Each piece had to be sprayed separately on the jams, the edges, and the interior of the body for each color. Then the car was totally assembled for painting so there'd be no variation in color. Every color change the car was disassembled sprayed the next color, and then re-assembled for spraying the entire assembly - taping off the inside of the window and hatch area each time, so there'd be no color change or over-spray on the interior, after it had been sprayed.

Once the last coat of pearl was applied to the entire assembly, it was allowed to dry for a half hour, then the car was un-taped, disassembled, and each piece was set on it's own holder, and then sprayed with 6 coats of catalyzed clear - 2 sets of being sprayed 3 times.

SPRAYED WITH THE CLEAR WITH THE PARTS SEPARATED because I didn't want the clear to "BRIDGE" across moving features, like the doors, hatch or hood, and I could spray all the jams and other body features and details at the same time.

That's a good 10 to 12 hour day, figuring in mixing the paints and a few other steps.

LASTLY

THERE'S NO PURPLE POND - If you screw up any of these mentioned steps , you better know how to fix it. If there's moving feature's like opening hood and doors and such, you've probably blown it, because any gap built in for paint will disappear on a redo, unless you're prepared for a lot of sanding and completely starting over .

But when it's done right, and I messed up sevaral in the beginning, you'll have a model to be proud of, and you'll have learned a major new stage in your building techniques and skills, and you'll be able to help others ready to move up into that next stage where you are.

In my WATER-BASED CHROME SYSTEM there are 5 separate catalyzed urethane systems.

It's an, 8 stage, 4 step system, that has 17 chemicals and takes four days of spraying to complete.

That's the level a person can go to if they desire, OR ARE CRAZY ENOUGH .

So now, let's hopefully hear from some of you.

Any advise or questions gladly welcome, or if I've left something out .

Edited August 2, 2009 by Treehugger Dave

[MonoPed]

You forgot to mention the safety precautions needed for catalyzed materials. They are a totally different animal than solvent based materials, and can cause great harm if inhaled. You MUST use a respirator rated for catalyzed materials to protect your lungs...

[nitrojunkie]

As Dave stated above the House Of Kolor line is a very well engineered system and is for the most part a totally compatible system.I love the UC -35 Klear and have used it on models before but for me its overkill for my models.However it is probably the best clear available today.My most involved paint job so far was my Honda Civic Hatchback that I did in Oriental blue Kandy over Silver white Marbelizer with the Kandy mixed in SG-100 and cleared with UC-35.Now no doors were opened up or anything other than the hood as supplied in the kit.But I completed this (once the black sealer had cured as specified in the tech book )in about 2 1/2 hrs.A word of caution when using UC-35 you have to spray an adjacent panel of some type to check the condition of the clear in its flashing stage." The paint (clear) should be sticky and not string when touched at the wettest point before the next coat is applied."What this means is you stick your finger or something into clear that was applied at the same time as your car if when you lift it it does not leave spider web looking strings you are ready to apply the next coat you must touch a new spot everytime when monitoring for this stage.Too soon you have a risk of solvent pop.Too late and it will lift or wrinkle, at that point its trashed! Here is a pic of the Civic it has been posted before on this forum.

[Fuel Coupe]

Yea Dave how about the safety aspect , Make sure you have a good respirator and, and.... I'm just busting your balls..

I just switched to Urethane clear and yes its a bit more involved but the final product outweighs the labor.

I think for most who haven't tried it is because of the unknown and how much emphasis is put on the safety issues around it. But if you dig you will find that ALL paints that are sprayed have their own inherent dangers.

Personally I wont spray anything but urethane as a final coat now. Its pretty easy as far as mixing and spraying. You stated it yourself that once you start to spray it you need to stay with it until its done....

I think the best way to see if you like it is to do what I did and go to your paint jobber and buy it in a two part spray can and give it a go.

I found PPG offers a shop-line system that is pretty inexpensive and sprays pretty darn good. it laid down for me with no trouble at all. it was a pretty hot/humid day and it glassed out pretty well.

I used the Shop-line JC661 clear with the JH6680 medium topcoat hardener. less than $40 for a quart w/hardener mixed 2:1

I guess what I'm saying is don't be scared of it. I'm no professional painter, there are no snake oils here. Just protect yourself, But if you are spraying any solvent type paints :lacquers enamels etc, You should already be wearing a respirator RIGHT

My very first urethane paint job....

Edited August 2, 2009 by TxRat

[nitrojunkie]

it was a pretty hot/humid day and it glassed out pretty well.

The humidity actually helps it kick faster.

[Fuel Coupe]

it was a pretty hot/humid day and it glassed out pretty well.

The humidity actually helps it kick faster.

thats good to know. I know that humidity cause lacquer to blush although I haven't experienced it yet...

[old low&slo]

this is a great topic because I have been thinking about jumping up to urethane clear.

for me I am kind of leaning towards using the hok paint system. meaning their paint with their reducer, the sg100 intercoat

and the uc35 clear.

I have a couple questions about the HOK paint.

1. why is it a bad idea to use cheap thinner instead of the hok reducer ?

2. would it be compatible to use either duplicolor or plasticote primer with the hok paint ?

the reason I ask that is to try and keep costs down a little.

3. and lastly if time is a problem could you paint the car and then go back and clear later ?

thank you in advance for any help.

[nitrojunkie]

this is a great topic because I have been thinking about jumping up to urethane clear.

for me I am kind of leaning towards using the hok paint system. meaning their paint with their reducer, the sg100 intercoat

and the uc35 clear.

I have a couple questions about the HOK paint.

1. why is it a bad idea to use cheap thinner instead of the hok reducer ?

2. would it be compatible to use either duplicolor or plasticote primer with the hok paint ?

the reason I ask that is to try and keep costs down a little.

3. and lastly if time is a problem could you paint the car and then go back and clear later ?

thank you in advance for any help.

1,Trust me you want to use their reducer. I have used lacquer thinner before and got away with it but I don't recomend it and don't do it anymore.

2,I use Duplicolor Lacquer Primer filler and their primer sealer both in gray.I also use their white primer all lacquer have had no problems as long as the plastic is properly prepped.

3,With HOK's BC & FBC metallic bases clear should be applied within12 hrs if not apply SG-100. I have waited 24 hrs on models with no problems,I usually put SG-100 over all base coats let it dry decal if required let dry overnight and clear ASAP next morning.

Reducers: The HOK reducer is used in all of their products other than their lacquer system.I use RU-311 extensively but depending on your conditions you may need one of the others.

RU-300 70-80 Degrees F

RU-310 65-75 Degrees F

RU-311 75-85 Degrees F

RU-312 85-95 Degrees F used in warm humid conditions to increase flow time and leveling. Short and sweet stays sticky longer, better be in a clean environment or dustnibs galore.

Edited August 2, 2009 by nitrojunkie

[old low&slo]

1,Trust me you want to use their reducer. I have used lacquer thinner before and got away with it but I don't recomend it and don't do it anymore.

2,I use Duplicolor Lacquer Primer filler and their primer sealer both in gray.I also use their white primer all lacquer have had no problems as long as the plastic is properly prepped.

3,With HOK's BC & FBC metallic bases clear should be applied within12 hrs if not apply SG-100. I have waited 24 hrs on models with no problems,I usually put SG-100 over all base coats let it dry decal if required let dry overnight and clear ASAP next morning.

Reducers: The HOK reducer is used in all of their products other than their lacquer system.I use RU-311 extensively but depending on your conditions you may need one of the others.

RU-300 70-80 Degrees F

RU-310 65-75 Degrees F

RU-311 75-85 Degrees F

RU-312 85-95 Degrees F used in warm humid conditions to increase flow time and leveling. Short and sweet stays sticky longer, better be in a clean environment or dustnibs galore.

1st thanks very much for taking the time to respond. I really appreciate it.

interesting that the guys selling the black gold line at NNL EAST last year were the ones telling me to use cheap med. thinner.

well I will go ahead and get the reducer then. and it sounds like if you dont have the time to do the final clear right then you can buy a little time with the intercoat. I have a paint booth set up in the basement so I will have to check the temp down there. you guys have cleared up a lot of questions I had so thanks again

[E St. Kruiser50]

this is a great topic because I have been thinking about jumping up to urethane clear.

for me I am kind of leaning towards using the hok paint system. meaning their paint with their reducer, the sg100 intercoat

and the uc35 clear.

I have a couple questions about the HOK paint.

1. why is it a bad idea to use cheap thinner instead of the hok reducer ?

2. would it be compatible to use either duplicolor or plasticote primer with the hok paint ?

the reason I ask that is to try and keep costs down a little.

3. and lastly if time is a problem could you paint the car and then go back and clear later ?

thank you in advance for any help.

Glat to see so many people discussing this, and a lot of good feedback .

Here's my feedback on your three questions.

1) I'm assuming you're asking about lacquer thinner.

First it give's unpredictable results. People who say they have gotten good results with lacquer thinner, use the word"GOOD" as a relative term, and DO have problems from time to time.

Second, good reducers come with different number ratings for different temperature needs, and it does also make a difference as too predictability for results and a high quality finish. That's how the real time car painters do it, and it works.

Thirdly, why take a chance of messing up a whole project, all that time and expense, to save a few dollars and have to start over and then have to get the right reducer after all.

Why not just do it the way it was meant to be used.

If you can' afford it, just buy the paint supplies a little at a time until you have everything you need to do it right, and then you can do the job properly and feel good about it.

Even with the right materials you'll make mistakes learning, so why complicate an already complicated process even more, by using the wrong materials, and then having no idea at all what went wrong, if it does, and how to adjust to do it properly?

2)I had to learn the hard way about using the right primers under the urethane color coat.

Urethane paints are not compatible with lacquer primers, anymore than lacquer thinners are with urethane paints.

There will always be very unpredictable results not using the proper materials, that's why urethane primers are part of the "Urethane system".

Urethane primers act as a barrier coat so the urethane color top coat won't penetrate the lacquer primer, which it will, and attack the plastic and or the lacquer primer, which it will - TRUST ME.

I primer the body first with lacquer primer while doing body work, and when done lay down the urethane primer to seal the body work and prep the body properly for the color coat to adhere properly.

SEE THE RETRO-VETTE ARTICLE in this Julys issue, there is a complete tutorial on the whole urethane process, step by step.

3)Urethane has a 24 hour window to paint in. When you go past that, bad things start to happen.

Paint attacking itself, aligatoring, and so on

Once your into it, you stay there. PERIOD. Painting urethane has to be premeditated, not done as an after thought or on the "FLY" between other things.

You need to dedicate s specific amount of time for that particular project, because it's intense and needs your full attention to succeed .

[old low&slo]

dave thanks very much for replying.

and yes I did mean lacquer thinner. I am going to take the advise you guys have given and go the the whole urethane route primer and all. but that will take some time to get all the materials I will need but hey good things come to those that wait right . and I am a firm believer if your going to do something do it right or not at all. since I like to build mostly lowriders the hok paint is the direction I have been wanting to go.

I dont have a subscription to the mag so I will have to see if any of the shops around here carry it. I would like to read that article. the shops and newstands only carry the other one.

[Fuel Coupe]

dave thanks very much for replying.

and yes I did mean lacquer thinner. I am going to take the advise you guys have given and go the the whole urethane route primer and all. but that will take some time to get all the materials I will need but hey good things come to those that wait right . and I am a firm believer if your going to do something do it right or not at all. since I like to build mostly lowriders the hok paint is the direction I have been wanting to go.

I dont have a subscription to the mag so I will have to see if any of the shops around here carry it. I would like to read that article. the shops and newstands only carry the other one.

Attaboy!!!

[Foxer]

I am following this even though I do not expect to be using this paint anytime soon, if ever at all. Even so, this thread is immensely interesting.

I was close to asking in another urethane thread why the heck anyone would go to all this trouble when lacquers do such a nice job, but you all have answered that here .. the depth and brilliance.

One thing I don't understand is the 2-part nature. Is there a catalyst that has to be added when mixing? And if so, does it have a limited pot life? Maybe I'm just reading too much into this.

Edited August 3, 2009 by Foxer

[E St. Kruiser50]

I am following this even though I do not expect to be using this paint anytime soon, if ever at all. Even so, this thread is immensely interesting.

I was close to asking in another urethane thread why the heck anyone would go to all this trouble when lacquers do such a nice job, but you all have answered that here .. the depth and brilliance.

One thing I don't understand is the 2-part nature. Is there a catalyst that has to be added when mixing? And if so, does it have a limited pot life? Maybe I'm just reading too much into this.

Really good questions mike

There are three components always used, but differently in single stage than in two stage urethanes.

In single stage urethanes you mix all three components together at the same time - paint, reducer and catalyst - then spray. This comes out glossy and there is no need for a clear coat - Single stage.

Two stage is where you mix the paint and reducer together, spray it and it comes out flat. NO CATALYST.

Then you mix your clear gloss top coat with reducer and catalyst and spray that over your color base coat, and this 2nd stage gives you your gloss and added protection for the paint.

Single stage is usually a cheaper way to go because of way less paint and labor, but is more suceptable to oxidation and damage that can't be repaired as easily as a clear coat.

Hope this helps - dave

[Helipilot16]

Just a word of caution for those who care about safety; the only respirator rated for urethanes is a supplied air respirator. These can cost from $500 on up, and they require a dedicated compressor.