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A bitter lesson learned

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  • Member since
    August, 2008
  • From: Long Beach, CA
A bitter lesson learned
Posted by pathvet9 on Monday, September 02, 2019 10:01 AM

I am slowly finishing up a nice Tamiya kit of the Ducati motorcycle and reached the point of painting the cowlings.

I started with TS26 pure white and thought I was being smart to test the finish for reactivity to Krylon Clear Coat. All was fine so I used the Tamiya provided masks and then sprayed Italian Red TS8. Waited a day and then oversprayed with the Krylon ..... and screamed oh ..........   Super Angry

Guess the lesson is different colors of the same paint manufacturer react differently. 

Back to the prep and re-paint. Hoping that Testors Clear won't react with either paint.

Cheers, Jake

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Nuts to all but my Norfolk terrier is laughing

  • Member since
    August, 2019
  • From: Brisbane Australia
Posted by Josh_the_painter on Monday, September 02, 2019 2:31 PM

Ok thats an interesting problem. I can see the edge of the red lifting but not much else. Can you tell me if all the red played up or just the edges?

Also where the red is missing through the vents would you say it literally disintegrated or has it 'shriveled up'?

Josh

  • Member since
    August, 2008
  • From: Long Beach, CA
Posted by pathvet9 on Monday, September 02, 2019 3:02 PM
Josh - actually it is harder to tell than I thought from the picture but it actually sloughed in various places swell as the edge. In the middle of the red on the side cowls there are missing holes but the highlights obscure it. Thanks so taking a look.

Cheers, Jake

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Nuts to all but my Norfolk terrier is laughing

  • Member since
    April, 2003
  • From: USA
Posted by keavdog on Monday, September 02, 2019 3:14 PM

That sucks!  I built that kit but in all over italian red.  I swear, white and red paint jobs are the most difficult.   Otherwise, bike looks good!

Thanks,

John

  • Member since
    August, 2019
  • From: Brisbane Australia
Posted by Josh_the_painter on Monday, September 02, 2019 9:23 PM

pathvet9
Josh - actually it is harder to tell than I thought from the picture but it actually sloughed in various places swell as the edge. In the middle of the red on the side cowls there are missing holes but the highlights obscure it. Thanks so taking a look.
 

 

Soooo you were right to test the krylon beforehand and it didnt react so seems ok, the krylon isnt actually reacting with the red however. I almost guarantee you spray the red on its own and overcoat in krylon it wont react either. 

Paint is under an incredible amount of stress, it relies completely on its adhesion to the surface its being applied. As it dries and the molecules pull together as the solvents evaporate it literally shrinks. Whats happening is as you have applied the krylon, the solvents are soaking through the red layer and releasing its adhesion to the white layer. As the clear is shrinking starting to dry, its pulling the red coat it's trying to adhere to along with it. 

In short the krylons not really designed to work with the paint your using. It wouldnt matter how long you left the red to dry it would have mostly still happened. If using paint all of the same manufacturer it shouldnt have been a problem and the krylon is mostly ok over a straight/ not overlayed colour. Using a hobby based clear coat should be fine. Personally Ive been using wurth aerosols for clear with ok results so theres no need to stick with hobby specific paints, just need to find that other product that works for you. 

I hooe that gives you some insight.

Josh

  • Member since
    July, 2013
  • From: Chicago area
Posted by modelmaker66 on Monday, September 02, 2019 11:09 PM

Thanks for the information Josh! Stuff like that is what is so helpful on this site.

  • Member since
    August, 2008
  • From: Long Beach, CA
Posted by pathvet9 on Monday, September 02, 2019 11:37 PM
Josh - thanks so much for that information. I see what you are saying. So, do you think I would be OK with Testors Clear Coat instead?

Cheers, Jake

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Nuts to all but my Norfolk terrier is laughing

  • Member since
    August, 2019
  • From: Brisbane Australia
Posted by Josh_the_painter on Tuesday, September 03, 2019 7:00 AM

modelmaker66

Thanks for the information Josh! Stuff like that is what is so helpful on this site.

 

No worries mate Yes

 

pathvet9
Josh - thanks so much for that information. I see what you are saying. So, do you think I would be OK with Testors Clear Coat instead?
 

No problem! Unfortunately knowledge doesnt solve your problem but its nice to understand the process.

Its hard to say for the testors, all products will react differently and Testors seem to have a number of different clear coats each with differing chemical make ups. Unfortunately the only way you can be sure is to test. When you repaint your fairings perhaps do a couple of test panels at the same time to test your clear on? 

Since your already having solvent issues I would maybe steer clear of lacquer based clears as they can be awfully aggressive. 

Whichever way you go however let us know your results!

  • Member since
    June, 2014
  • From: New Braunfels , Texas
Posted by Tanker - Builder on Tuesday, September 03, 2019 10:57 AM

Hi;

      I usually use the Testors Clearcoat. Sometimes labeled as Boyd's Clear! I have never had a problem with it.Now ,for my paper( Or card Models) I use any craft Clear acrylic available,either Flat ,Semi-Gloss or Gloss. Never have had any problems with some of those on my regular models either.

  • Member since
    August, 2019
  • From: Brisbane Australia
Posted by Josh_the_painter on Friday, September 06, 2019 9:11 PM

So doing some reading and research I see the Tamiya basecoats are lacquer based. This confirms for me my previous conclusion as to what went wrong. Ive seen this same thing happen with adhesion promoters that contain a lacquer film. 

What may be a beneficial solution is to base and clear the white to seal off the lacquer then apply the red and reclear. 

I think the krylon or the testors clear will be fine if applied this way. The testors may be fine straight on top of both colours but again its not a process Ive tried so cannot suggest that being the answer. 

Again, looking foward to your results!

Josh

  • Member since
    August, 2008
  • From: Long Beach, CA
Posted by pathvet9 on Saturday, September 07, 2019 1:22 PM

Josh - I have closed shop for 2 months on the road but I am very thankful to hear your assessment.

A further glitch before i left as I forgot to paint the underside gloss black and now have some creeps.  Crying

So I will be taking it down and starting again in November. Thanks again for your help and I will keep you apprised. 

Cheers, Jake in Taos NM today

Cheers, Jake

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Nuts to all but my Norfolk terrier is laughing

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