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Author Topic: Paint reacting with itself?  (Read 3688 times)

tonyH

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Paint reacting with itself?
« on: March 01, 2015, 11:08:41 AM »

Can anyone help with an answer to this oddity?

I'm using Hycote white car primer over a previously painted Flower corvette where the previous paints have been rubbed down to a fair finish.
The first coat went on well but another coat or coats were needed.
After the second coat from the same can went on 99.9% was fine but small patches blistered as if a reaction had taken place.
I sanded the areas back and repeated a second coat to the affected areas. Same reaction in same places.

I'm due to start spraying the deck fittings but I'm obviously wary about doing so until I can sort this bit out.

Any ideas?

Tony {:-{
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Stavros

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Re: Paint reacting with itself?
« Reply #1 on: March 01, 2015, 03:02:19 PM »

Think theans lies in the old paint doesnt sound to be a automotive car paint


Dave
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tonyH

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Re: Paint reacting with itself?
« Reply #2 on: March 01, 2015, 04:00:09 PM »

Hi Dave,

The original paint on the hull was, as far as I remember, Tamiya on Halfords grey primer. The new primer comes from a range sold by a number of car spares/car accessory shops around and the first and almost 100% of the second and subsequent coats were fine. It's just the few small odd bits where the second coat has reacted with the first. It's not even in the odd corner where there could be a bit of latent solvent hanging around. I'm mystified %%

Tony
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Stavros

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Re: Paint reacting with itself?
« Reply #3 on: March 01, 2015, 07:52:35 PM »

You have answered your own question......TAMIYA .....it is an enamel paint.......cellulose and enamel will not mix.  I'll gtee you that is the problem


Dave
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tonyH

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Re: Paint reacting with itself?
« Reply #4 on: March 01, 2015, 09:35:32 PM »

Aye, I'm sure you're right Dave but I couldn't understand why the first coat of the new primer didn't react, only the second one. Murphy has something to do with it I'm sure O0

Cheers

Tony
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essex2visuvesi

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Re: Paint reacting with itself?
« Reply #5 on: March 01, 2015, 11:33:36 PM »

you could try a coat of this
http://www.jawel.co.uk/index.php?main_page=product_info&products_id=3248
best thing would be to strip back the paint as far as possible and try again
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tonyH

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Re: Paint reacting with itself?
« Reply #6 on: March 02, 2015, 09:27:53 AM »

Cheers Essex,

I've taken the sanding back route because it the reaction only occurred on about 10 sq.cm in total over 0.5 sq.metres so it wasn't a major job. It's just that I was intrigued by the way a second coat reacted with the first coat of the same paint.

Thanks to you and Dave,

Tony
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NFMike

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Re: Paint reacting with itself?
« Reply #7 on: March 02, 2015, 11:45:49 AM »

It's just that I was intrigued by the way a second coat reacted with the first coat of the same paint.

You don't give a lot of detail. How long between coats? 24 hours ... touch dry? If the latter then the first coat might have mostly evaporated its solvents but could also have just started to affect the underlying paint. The solvents in the next coat then have a ready softened target to go at (Dave keeps telling us primers are porous) and bingo - you have a problem.
Even after 24 hours it's possible that the activity of the first primer coat has irrevocably affected the underlying paint and as above the next batch of solvent can react more easily with it.

morley bill 1

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Re: Paint reacting with itself?
« Reply #8 on: March 02, 2015, 12:41:29 PM »

tamya is normally an acrylic paint..Bill.
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morley bill 1

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Re: Paint reacting with itself?
« Reply #9 on: March 02, 2015, 12:48:36 PM »

Tony if the first coat did/nt react with the Tamiya I see no reason the second should it/s possible you have got some oil or silicone contamination on the paint this has happened to me before  hope this helps.. Bill.....
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Stavros

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Re: Paint reacting with itself?
« Reply #10 on: March 02, 2015, 01:05:12 PM »

You don't give a lot of detail. How long between coats? 24 hours ... touch dry? If the latter then the first coat might have mostly evaporated its solvents but could also have just started to affect the underlying paint. The solvents in the next coat then have a ready softened target to go at (Dave keeps telling us primers are porous) and bingo - you have a problem.
Even after 24 hours it's possible that the activity of the first primer coat has irrevocably affected the underlying paint and as above the next batch of solvent can react more easily with it.


couldnt have put it better myself




Dave
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tonyH

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Re: Paint reacting with itself?
« Reply #11 on: March 02, 2015, 07:42:39 PM »

From the last few posts, I reckon it was small patches of unhardened first coat rather than a reaction with the underlying old paint. The areas were in on the flats of the plate detail rather than the corners/crevises and I just hadn't allowed for the fact that the paint was at the minimum safe temperature. I'd left the recommended time between coats but little more so............... :embarrassed:

New coats after a rub down are fine so I will proceed...................with caution!!!!!!!!!!!

Thanks again

Tony
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Stavros

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Re: Paint reacting with itself?
« Reply #12 on: March 02, 2015, 09:16:56 PM »

Read my post about painting in the painting section
 
 
Dave
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