Paint reaction question

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georgesheppard
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Paint reaction question

Post by georgesheppard » Tue Feb 16, 2021 11:06 am

Hello,

While putting the finishing touches on my latest carriage build there seems to have been some reaction between the paint and clear coat. It was a bit cold but not freezing.
IMG_0363.jpg
I actually don't mind the finish on the roof but would be somewhat annoyed if that happened on body work. It seems to be Plastikote, I've had a similar issue when spraying over types of paint over the top of Plastikote.

Anyone had similar experience?

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Andrew
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Re: Paint reaction question

Post by Andrew » Tue Feb 16, 2021 11:23 am

That looks pretty good on the roof - I'm sure I've seen real carriage roof canvases that have wrinkled into that sort of pattern...

Sorry, can't advise on the caus though - different types of paint? I thought the cold tends to cause running or blooming rather than that reaction?

All the best,

Andrew.

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philipy
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Re: Paint reaction question

Post by philipy » Tue Feb 16, 2021 11:54 am

It looks more like paint reaction than environment to me. You mention Plastikote but I'm not sure if that was the clear varnish or the base paint? Either way, what paint type/manufacturer was the other component, and how long did you leave it to dry between the base colour and the overspray?

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Re: Paint reaction question

Post by georgesheppard » Tue Feb 16, 2021 12:21 pm

I used the following paints on the roof

Rust-Oleum grey primer https://www.amazon.co.uk/Rust-Oleum-AE0 ... 13-6589445
Plastikote matt grey https://www.amazon.co.uk/gp/product/B00 ... UTF8&psc=1
Rust-Oleum Matt Lacquer https://www.amazon.co.uk/gp/product/B01 ... TF8&psc=1p

Not had any issues with Hycote or other Rust-Oleum colours (Satin Black) so far. Seems perhaps Plastikote doesn't play well with the other products I'm using. I used a blue Plastikote spray paint on the overlays and there is a tiny amount of the 'reaction' present there. Seems strange it's not everywhere..

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Re: Paint reaction question

Post by philipy » Tue Feb 16, 2021 1:23 pm

As a rule of thumb, I'd always try to use one manufacturer. The problem is quite likely linked to the solvent systems used by each brand being different and one reacting with the other..
The only exception would be using when using acrylic paints.

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Re: Paint reaction question

Post by Jimmyb » Tue Feb 16, 2021 1:29 pm

I have had issues (a few years ago now) with varnish/lacquer, even though the top coat was supposedly compatible. One piece of advice was the ensure the base colour had dried properly i.e. at least 7 days, so these days I never put my clear coat on until at least 7 days, normally longer.

You also mention temperature, a number of spray cans recommend temperatures above 10 degrees, that is the paint, the model and the atmosphere, but this I understand is to ensure adhesion.

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Re: Paint reaction question

Post by Peter Butler » Tue Feb 16, 2021 2:55 pm

philipy wrote:
Tue Feb 16, 2021 1:23 pm
The problem is quite likely linked to the solvent systems used by each brand being different and one reacting with the other..
The only exception would be using when using acrylic paints.
I absolutely agree with Philip and every time I have been asked about paints and lacquers I always steer towards acrylics, whether spray or brush.
Also, the ones from Amazon, which George supplied the link to, are more expensive than the ones I have mentioned previously, Hycote primers and lacquers are available on-line, often free post too!
The best things in life are free.... so why am I doing this?

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Re: Paint reaction question

Post by ge_rik » Tue Feb 16, 2021 3:21 pm

I've had reactions like that when mixing brands in the past. I now tend to stick with the same brand of primer, topcoat and lacquer to be safe. Failing that, I spray on to a small test piece before spraying on to a model. The benefit of hindsight. :?

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georgesheppard
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Re: Paint reaction question

Post by georgesheppard » Tue Feb 16, 2021 5:06 pm

Thanks for the input everyone! I think I'll try and stick to the same brand where possible in the future!

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Re: Paint reaction question

Post by GTB » Wed Feb 17, 2021 8:17 am

georgesheppard wrote:
Tue Feb 16, 2021 5:06 pm
Thanks for the input everyone! I think I'll try and stick to the same brand where possible in the future!
The problem may be incompatible paint types, which will be due to the solvents used, but there is also another mechanism that gives that sort of finish.

There is a special paint called 'wrinkle finish' ( 'Krinkle Kote' to the heathens in the US), that was once common on electrical cabinets and some car parts. It works by applying a second coat of paint over a base coat that is only part cured.

Given the temperatures currently being achieved north of the equator, it is possible that the colour coat hadn't fully cured and was wrinkled by the clear coat.

Not an issue here, it got to 30C in my workshop today, before I gave up and came inside for an icy pole. Even with the local climate, I still leave paint for at least a week before applying another coat.

Regards,
Graeme

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Re: Paint reaction question

Post by GAP » Fri Feb 19, 2021 8:47 pm

georgesheppard wrote:
Tue Feb 16, 2021 12:21 pm
I used the following paints on the roof

Rust-Oleum grey primer https://www.amazon.co.uk/Rust-Oleum-AE0 ... 13-6589445
Plastikote matt grey https://www.amazon.co.uk/gp/product/B00 ... UTF8&psc=1
Rust-Oleum Matt Lacquer https://www.amazon.co.uk/gp/product/B01 ... TF8&psc=1p

Not had any issues with Hycote or other Rust-Oleum colours (Satin Black) so far. Seems perhaps Plastikote doesn't play well with the other products I'm using. I used a blue Plastikote spray paint on the overlays and there is a tiny amount of the 'reaction' present there. Seems strange it's not everywhere..
I had a similar problem with Rustoleum I sprayed one coat and waited 2 days for it to dry and then applied a second coat and it reacted badly with a similar appearance to what you have.
I contacted Rustoleum and their rep told me that it was caused by the solvent in the second coat dissolving the first coat, she advised me to apply only one thick coat instead of 2 lighter coats in future.
So from my experience I would suggest that the lacquer solvent has attacked the Plastikote and maybe even the Primer.

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Re: Paint reaction question

Post by georgesheppard » Sun Feb 21, 2021 5:07 pm

GAP wrote:
Fri Feb 19, 2021 8:47 pm
georgesheppard wrote:
Tue Feb 16, 2021 12:21 pm
I used the following paints on the roof

Rust-Oleum grey primer https://www.amazon.co.uk/Rust-Oleum-AE0 ... 13-6589445
Plastikote matt grey https://www.amazon.co.uk/gp/product/B00 ... UTF8&psc=1
Rust-Oleum Matt Lacquer https://www.amazon.co.uk/gp/product/B01 ... TF8&psc=1p

Not had any issues with Hycote or other Rust-Oleum colours (Satin Black) so far. Seems perhaps Plastikote doesn't play well with the other products I'm using. I used a blue Plastikote spray paint on the overlays and there is a tiny amount of the 'reaction' present there. Seems strange it's not everywhere..
I had a similar problem with Rustoleum I sprayed one coat and waited 2 days for it to dry and then applied a second coat and it reacted badly with a similar appearance to what you have.
I contacted Rustoleum and their rep told me that it was caused by the solvent in the second coat dissolving the first coat, she advised me to apply only one thick coat instead of 2 lighter coats in future.
So from my experience I would suggest that the lacquer solvent has attacked the Plastikote and maybe even the Primer.
Good to know! The strange thing is I painted another carriage with the same paints and had no reaction what soever. I have a feeling perhaps I waited longer between coats (or perhaps shorter?!)

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Re: Paint reaction question

Post by GAP » Mon Feb 22, 2021 8:58 pm

georgesheppard wrote:
Sun Feb 21, 2021 5:07 pm
GAP wrote:
Fri Feb 19, 2021 8:47 pm
georgesheppard wrote:
Tue Feb 16, 2021 12:21 pm
I used the following paints on the roof

Rust-Oleum grey primer https://www.amazon.co.uk/Rust-Oleum-AE0 ... 13-6589445
Plastikote matt grey https://www.amazon.co.uk/gp/product/B00 ... UTF8&psc=1
Rust-Oleum Matt Lacquer https://www.amazon.co.uk/gp/product/B01 ... TF8&psc=1p

Not had any issues with Hycote or other Rust-Oleum colours (Satin Black) so far. Seems perhaps Plastikote doesn't play well with the other products I'm using. I used a blue Plastikote spray paint on the overlays and there is a tiny amount of the 'reaction' present there. Seems strange it's not everywhere..
I had a similar problem with Rustoleum I sprayed one coat and waited 2 days for it to dry and then applied a second coat and it reacted badly with a similar appearance to what you have.
I contacted Rustoleum and their rep told me that it was caused by the solvent in the second coat dissolving the first coat, she advised me to apply only one thick coat instead of 2 lighter coats in future.
So from my experience I would suggest that the lacquer solvent has attacked the Plastikote and maybe even the Primer.
Good to know! The strange thing is I painted another carriage with the same paints and had no reaction what soever. I have a feeling perhaps I waited longer between coats (or perhaps shorter?!)
Reading the instruction on my can of Rustoleum 2X it says "Apply second clear coat or clear coat within 1 hour or after 48 hours. Apply clear in 2-3 light coats a few minutes apart" I think there is an error in the instructions with one to many clears in them (in Bold).
Also there is a Note "On plastic, maximum paint adhesion and durability is achieved in 5-7 days"
Temperature is also a contributing factor, "Times based on 21C - 50% relative humidity. Allow more time at cooler temperatures." so perhaps waiting a little longer may help.
I do not use Rustoleum any more I use auto touch up paint from Repco in Aust (Halfords in UK.)

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Re: Paint reaction question

Post by Jimmyb » Tue Feb 23, 2021 10:46 am

I have often had difficulties in the past with lacquer, and over the last couple of years with my move to garden railways again encountered the odd difficulty. More often as not the slow drying, even in the UK summer, a warm (20 degrees +) and some paint seems to take hours to dry, yet on another day same brand and no issues. This of course could be related to the sprayer (me) but I feel other factors also contribute, e.g. base coat and how dry it is, I now wait at least 7 days; temperature, I try not to spray below 12 degrees (spraying in winter is sometime a necessary); humidity, though not sure if low or high RH is best.

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Re: Paint reaction question

Post by GAP » Tue Feb 23, 2021 8:35 pm

Jimmyb wrote:
Tue Feb 23, 2021 10:46 am
I have often had difficulties in the past with lacquer, and over the last couple of years with my move to garden railways again encountered the odd difficulty. More often as not the slow drying, even in the UK summer, a warm (20 degrees +) and some paint seems to take hours to dry, yet on another day same brand and no issues. This of course could be related to the sprayer (me) but I feel other factors also contribute, e.g. base coat and how dry it is, I now wait at least 7 days; temperature, I try not to spray below 12 degrees (spraying in winter is sometime a necessary); humidity, though not sure if low or high RH is best.
Humidity is a factor that is often overlooked most manufacturers use 50% as their standard, but unless you have a controlled environment (air conditioned area) that generally is not achievable.
I think low would be better for drying paint (less moisture in the air).

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