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Author Topic: Paint Compatibility - Again!  (Read 5567 times)

Marc St Hilaire

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Paint Compatibility - Again!
« on: May 02, 2011, 05:44:13 PM »

Sorry but now I am really confused!

I am building a model in balsa, ply and plasticard, mainly. I have primed the wooden hull using ordinary household white primer - oil based. I wish to finish the model using Humbrol Grey 64 from a spray can. But this claims to be Acrylic (waterbased?)- so not compatable with the OB primer, after reading some threads on here. However, as a test I sprayed some of the paint into the cap. It's not waterbased. So I then srayed some on the OB white as a test. No problem. No cracking, no crazing.

My question is: is it ok to spray Humbrol acrylic over oil bases paints? If I want to touch up with Grey 64 from a tinlet (Enamel - oil based {?}) i.e. oil based over acrylic, is that ok?

I've got some cans of a very nice cellulose paint but I'm not even thinking about using those.  :-)

Thanks!

Chris.
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triumphjon

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Re: Paint Compatibility - Again!
« Reply #1 on: May 02, 2011, 09:02:17 PM »

oil base should work over the acrylic but not usually the other way around !
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nhp651

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Re: Paint Compatibility - Again!
« Reply #2 on: May 02, 2011, 09:04:57 PM »

if you spray acrylic or cellulose onto oil based and enamel paints, you'll get an orange peel effect marc.

acrylics and cellulose dry basically by evaporation, and by etching into the primed surface.
by painting onto oil and enamel based...the paint etches into the under layer and picks at it giving that unfortunate effect.
you can though paint the oils and enamels onto cellulose and acrylic paints without problem.
neil
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triumphjon

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Re: Paint Compatibility - Again!
« Reply #3 on: May 02, 2011, 09:08:18 PM »

celly wont work being over painted onto enamels it lifts  & makes a huge mess ! ive seen it happen .
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nhp651

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Re: Paint Compatibility - Again!
« Reply #4 on: May 02, 2011, 09:13:19 PM »

 that's what i said, tj


you can though paint the oils and enamels onto cellulose and acrylic paints without problem
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Marc St Hilaire

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Re: Paint Compatibility - Again!
« Reply #5 on: May 03, 2011, 10:22:52 AM »

Thanks everyone. I don't intending using the cellulose - too complicated!

I always thought acrylic paint was waterbased, from my old days painting wargaming model soldiers. I have just test sprayed my Humbrol paint and its definitely not waterbased. It doesn't like white spirit thinners either: it sort of curdles. 

When I sprayed the acrylic over the oil based white, as a test, it seemed ok but it was on balsa, so maybe an orange peel effect was hidden by the less than mirror like finish to the wood.

OK. So lesson learned. Don't use Jewsons Professional undercoat white as a base coat. Pity, it was very good as a primer filler. And cheap. :-)

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wartsilaone

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Re: Paint Compatibility - Again!
« Reply #6 on: May 03, 2011, 10:50:01 AM »

I have found that when using Humbrol spray paint you can use enamel over acrylic but you can't use acrylic over enamel especially when using varnish. something to do with how quick the paint dries.

Ali.
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Stavros

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Re: Paint Compatibility - Again!
« Reply #7 on: May 03, 2011, 01:09:35 PM »

ACRYLIC OVER ENAMEL..............................................no way it will react

CELLULOSE OVER ENAMEL..........................................no way it will react

2 PACK CAR PAINT OVER ENAMEL...............................yes and no....depends how old the enamel is

ENAMEL OVER CELLULOSE/ACRYLIC/2PACK...................no problem at all

VARNISHES..............................................................as long as they are waterbased or enamels they will go over anything

GOLDEN RULE OF PAINTING.......................................keep to the same systen DONT MIX AND MATCH........KEEP TO THE SAME MANUFACTERER


Want to know more then dont hessitate to ask....over 30 yrs in the motor trade so i do know a thing or 2 about paint


stav







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