How much can you thin Rustoleum?

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How much can you thin Rustoleum?

Post by roller painter on March 14th 2013, 9:47 pm

How much can you thin rustoleum? I know the thinning of this paint (50% Paint with 50% Mineral Spirits), will help it self level better, and flow out better with a roller, and possibly slow down the drying process, to dry flatter. But does this thinner paint mixture become less strong and less durable after drying? Or does the mineral spirits just evaporate away and leave the rustoleum paint just as strong as unthinned rustoleum after drying? To further ask this question, I want to ask: Obviously a mixture of 30% Rustoleum Paint mixed with 70% Mineral Spirits, would give much less coverage and might cause runs and sags, but once the paint has dried and the mineral spirits have evaporated away, will it be just as strong and durable as unthinned Rustoleum?

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Re: How much can you thin Rustoleum?

Post by roller painter on March 14th 2013, 6:10 pm

What about thinning automotive paint? Like an Acrylic Enamel, or an Acrylic Urethane Enamel? If you thin the auto paint more than the directions say to thin the auto paint, could anything go wrong? Obviously you would get much less coverage, and possibly runs and sags, but can anything else serious happen to the (more thinned) auto paint once it is cured and dried? Will the (more thinned) auto paint still be as strong and durable, (once it has dried and cured),
as the same exact auto paint that was (properly/less thinned) according to the exact directions? What if the directions say to use 4 parts auto paint and 2 parts auto paint thinner, and instead you try to mix it to: 4 parts auto paint and 4 parts or even 5 parts auto paint thinner? Could the (more thinned) auto paint become more soft and less strong once dried and cured, than a properly thinned auto paint per the exact instructions? Could the thinned auto paint chip easier or flake off easier if thinned too much, once dried and cured?

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Re: How much can you thin Rustoleum?

Post by Samilcar on March 17th 2013, 3:02 pm

roller painter wrote:Or does the mineral spirits just evaporate away and leave the rustoleum paint just as strong as unthinned rustoleum after drying?

Yes. In fact, one layer of unthinned rustoleum will be softer than one 50/50 thinned layer of rustoleum. When one layer of unthinned oil based paint is applied, it is usually thick enough to fully cover what is underneath it. However, after 24 hours it forms a "skin" as only the outer surface of this one thick layer has dried (the mineral spirits have fully evaporated from this outer skin only). This traps the unevaporated mineral spirits beneath this outer skin. This leaves the paint relatively soft, which is an advantage in that it is also very flexible, making it resistant to cracking. However, it cannot be buffed or polished to a full shine like harder paints, as buffing breaks through this fully dried outer skin and reveals the uncured surface beneath. This makes the paint appear duller and "smeared" rather than shinier. One thick layer of oil based enamel will eventually fully dry as the mineral spirits slowly evaporate through this outer skin, but this can take years to happen.

The beauty of using the 50/50 thinned oil enamel is that it makes a single layer of applied paint extremely thin. This is bad in that it doesn't cover what is underneath it very well, meaning multiple coats are required. It is good in that this one, very thin, layer fully dries in 24 hours, leaving no uncured layer underneath of it.

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Re: How much can you thin Rustoleum?

Post by HMCFab9 on April 11th 2013, 12:03 am

I don't have a good answer, but when I sprayed gloss black rustoleum & thinned it enough to spray decent, it didn't have the same good gloss as when I brushed it.

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