Repairing 'crazed' paint
- gregh
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Repairing 'crazed' paint
I'm always having problems using spray cans of paint on styrene.
Sometimes - just sometimes, the paint crazes like this In this case I sprayed directly onto the bare styrene. Usually I spray grey primer first and it 'rarely' crazes.
I've searched for the reason, but drawn a blank. I've tried ensuring the can is warm enough (not a problem in Sydney in summer).
I've wondered if it is high humidity (it IS in Sydney). I've washed the styrene parts in soap and water and rinsed well but still SOMETIMES it crazes.
And usually the solution is to sand it all back and hope it works next time. Bit of a pain if I've spent hours adding rivet detail!
Anyhow, I have managed to find a part solution - I took a cotton tip (?) and dipped it in turps and washed it over the crazed paint. It dissolves and makes the paint 'flow' into the cracks.
the picture looks worse that it is - just use lots of turps so it 'flows'.
Not a perfect job, especially if you want a perfect finish.
But in this case of the bogie, it allowed a quick fix. Here's the result.
Sometimes - just sometimes, the paint crazes like this In this case I sprayed directly onto the bare styrene. Usually I spray grey primer first and it 'rarely' crazes.
I've searched for the reason, but drawn a blank. I've tried ensuring the can is warm enough (not a problem in Sydney in summer).
I've wondered if it is high humidity (it IS in Sydney). I've washed the styrene parts in soap and water and rinsed well but still SOMETIMES it crazes.
And usually the solution is to sand it all back and hope it works next time. Bit of a pain if I've spent hours adding rivet detail!
Anyhow, I have managed to find a part solution - I took a cotton tip (?) and dipped it in turps and washed it over the crazed paint. It dissolves and makes the paint 'flow' into the cracks.
the picture looks worse that it is - just use lots of turps so it 'flows'.
Not a perfect job, especially if you want a perfect finish.
But in this case of the bogie, it allowed a quick fix. Here's the result.
Greg from downunder.
The Sandstone & Termite's website: https://members.optusnet.com.au/satr/satr.htm
The Sandstone & Termite's website: https://members.optusnet.com.au/satr/satr.htm
- Tropic Blunder
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Re: Repairing 'crazed' paint
Greg,
I'm not trying to be clever, but when you say turps, I assume you mean 'white spirit' not actual turpentine proper?
I'm not trying to be clever, but when you say turps, I assume you mean 'white spirit' not actual turpentine proper?
Philip
Re: Repairing 'crazed' paint
Handy tip, Greg. Thanks.
This has happened to me a couple of times. On both occasions, it was when the coat I was applying reacted badly with paint which was underlying it. Very frustrating, particularly when it's on a loco body with a lot of rivet detailing, so almost impossible to rub down without having to remove and replace all the rivet details. If it happens again, I'll give this technique a try.
Rik
This has happened to me a couple of times. On both occasions, it was when the coat I was applying reacted badly with paint which was underlying it. Very frustrating, particularly when it's on a loco body with a lot of rivet detailing, so almost impossible to rub down without having to remove and replace all the rivet details. If it happens again, I'll give this technique a try.
Rik
- gregh
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Re: Repairing 'crazed' paint
Here in Oz, it's full name is Mineral Turpentine, but called turps by everyone. It can be used to thin enamel paint and for cleaning brushes.
Don't know what white spirit is.
Greg from downunder.
The Sandstone & Termite's website: https://members.optusnet.com.au/satr/satr.htm
The Sandstone & Termite's website: https://members.optusnet.com.au/satr/satr.htm
Re: Repairing 'crazed' paint
Depends on what you lot call 'White Spirit'.........
'Turps' is 'Mineral Turpentine', a petrochemical solvent, in common use here in Oz for thinning enamel paint and cleaning the paint brush when you finish. As you say, not the same as the 'Turpentine' used by artists, which is distilled from plants. Alhough 'turps' is sometimes labelled as 'Turpentine Substitute'.
Here in Oz 'White Spirit' is a different petrochemical solvent with a higher flashpoint and lower aromatic content, sold for household use as a dry cleaner.
I keep a bottle of both in the workshop, Turps for cleaning paint brushes and White Spirit for use as a degreaser.
The high aromatic content of turps means it is a polystyrene solvent. If your 'White Spirits' can stick polystyrene together, it should do the same job as the turps described by Greg.
Graeme
Re: Repairing 'crazed' paint
Thanks guys. i think we are all on the same page. It used to be called "Turps substitute" here. However these days there are products called "Low odour white spirit" which smell different and don't have as vicious effect on plastics,so might not be as effective in this application.
Philip
Re: Repairing 'crazed' paint
We've got something called 'Low Odour Turps' which is much the same as the 'White Spirit' sold by the same company. OK as a degreaser, but not my first choice for cleaning paint brushes. Marketing Depts in action........
Re: Repairing 'crazed' paint
As Rik reported it is usually due to the solvents in the top coat attacking the layer under it. There are paint systems available deliberately designed to give the same effect for instant ageing of furniture.
The grey primer you use is probably more resistant to the paint solvents in the top coat than polystyrene is, especially once the primer is fully cured. The primer then acts as a resist layer and stops the polystyrene underneath from being attacked by the paint solvent.
How much cracking you get would depend on how wet the top coat goes on, what solvents the paint manufacturer used, as well as how well the primer had cured before the top coat was applied.
Regards,
Graeme
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