# acrylic paint curing time



## jason123 (Jul 2, 2009)

I'm looking into opinions on paint curing time. I have done a hand painted sign. Exterior aura semi gloss. I'm want to clear it with this 
https://www.kbs-coatings.com/DiamondFinish-Clear.html

It is a oil /solvent base whichever of that makes more sense. It's not water based. 

It says as long as the paint is fully cured it can be applied over acrylic. I know by specs it takes a month to cure, wondering if two weeks would be fine. I'm going to to tests patches to see before I apply it.


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## NACE (May 16, 2008)

A full cure foremost water based acrylics is 30 days. If you are applying an alkyd over it it should be dry for at least 14 days so that ammonia and alkyd do not react and cause the acrylic to yellow. As I have said before the definition of cure is when a coating reaches its full abrasion and chemical resistance. Dry is when the solvent has evaporated and has escaped from the film. In the case of water based acrylics water needs to evaporate and coalescence starts to take place to form a film. In the case of alkyds the solvent, usually mineral spirits, needs to escape and oxidation takes place.


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## Damon T (Nov 22, 2008)

NACE said:


> A full cure foremost water based acrylics is 30 days. If you are applying an alkyd over it it should be dry for at least 14 days so that ammonia and alkyd do not react and cause the acrylic to yellow. As I have said before the definition of cure is when a coating reaches its full abrasion and chemical resistance. Dry is when the solvent has evaporated and has escaped from the film. In the case of water based acrylics water needs to evaporate and coalescence starts to take place to form a film. In the case of alkyds the solvent, usually mineral spirits, needs to escape and oxidation takes place.




Nace what is the typical cure time for alkyds? I'm wondering especially in relation to coatings like BM Advance. I think that is a soybean oil resin but not sure. Also it seems like it would be hard to know when a coating has reached its full abrasion and chemical residence. At least for this OP's purpose. I haven't seen full cure time listed on a TDS. Seems like good info to provide. 
Thanks again for a helpful post. I appreciate your posts.


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## jason123 (Jul 2, 2009)

Thanks nace for the reply.


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## jason123 (Jul 2, 2009)

Oh yeah another question,, so if you coat it with a clear coat before its technically done curing does that then stop that layer from curing?


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## NACE (May 16, 2008)

jason123 said:


> Oh yeah another question,, so if you coat it with a clear coat before its technically done curing does that then stop that layer from curing?


 
Advance is a true alkyd that is a proprietary resin. Alkyds typically take 14 days to cure however Advance says up to 30 for full hardness and sheen development. Putting something over another coating doesn't necessarily slow or impede the curing process as coalescence, oxidation, and solvent evaporation are all taking place. Think of a paint film as one piece of Swiss cheese. One coat has lots of holes with from solvent evaporation as the film forms. As you put more pieces of cheese on, the holes begin to get smaller and less aligned until a monolithic film is formed. This is a general description as many different resin types have different characteristics or purposes. But this remains fairly true for standard architectural coatings. I was always taught latex, fast dry slow cure, oil, slow dry fast cure. the faster dry the more brittle a film, the higher the sheen or finish the more brittle.


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## jason123 (Jul 2, 2009)

God I love paint science.


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## PRC (Aug 28, 2014)

NACE said:


> Advance is a true alkyd that is a proprietary resin. Alkyds typically take 14 days to cure however Advance says up to 30 for full hardness and sheen development. Putting something over another coating doesn't necessarily slow or impede the curing process as coalescence, oxidation, and solvent evaporation are all taking place. Think of a paint film as one piece of Swiss cheese. One coat has lots of holes with from solvent evaporation as the film forms. As you put more pieces of cheese on, the holes begin to get smaller and less aligned until a monolithic film is formed. This is a general description as many different resin types have different characteristics or purposes. But this remains fairly true for standard architectural coatings. I was always taught latex, fast dry slow cure, oil, slow dry fast cure. the faster dry the more brittle a film, the higher the sheen or finish the more brittle.


Great info, thanks. So being a true alkyd, will Advance achieve the same level of durability/hardness as a regular oil? And is there different qualities of alkyd resins as there is acrylic?


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## NACE (May 16, 2008)

Advance will achieve the same hardness but it will take up to 30 days to achieve full hardness and finish. There are different alkyd resins. Alkyd is the generic for alcohol and acid. There are phenolic's, chains stop alkyds, and many other cocktails of various oils that are categorized as oil. Menhaden, (Bunker) is an excellent fish oil for rust inhibition.


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## PACman (Oct 24, 2014)

NACE said:


> Advance is a true alkyd that is a proprietary resin. Alkyds typically take 14 days to cure however Advance says up to 30 for full hardness and sheen development. Putting something over another coating doesn't necessarily slow or impede the curing process as coalescence, oxidation, and solvent evaporation are all taking place. Think of a paint film as one piece of Swiss cheese. One coat has lots of holes with from solvent evaporation as the film forms. As you put more pieces of cheese on, the holes begin to get smaller and less aligned until a monolithic film is formed. This is a general description as many different resin types have different characteristics or purposes. But this remains fairly true for standard architectural coatings. I was always taught latex, fast dry slow cure, oil, slow dry fast cure. the faster dry the more brittle a film, the higher the sheen or finish the more brittle.


Are you sure about that? Seems like a pretty general statement.


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## NACE (May 16, 2008)

It may slow it down, but since most paint films are very thin it may not effect it as much as surface and air temps, RH and Dew point. You could be correct but other factors apply as well.


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## PACman (Oct 24, 2014)

NACE said:


> It may slow it down, but since most paint films are very thin it may not effect it as much as surface and air temps, RH and Dew point. You could be correct but other factors apply as well.


I'm thinking along the lines of putting an enamel over an un-cured lacquer or visa versa. If you spray a thin coat of a quick drying lacquer over and un-cured enamel for example, doesn't it hinder the cure if the enamel? I know i'm nitpicking.


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## NACE (May 16, 2008)

thermoplastic coating vs thermo setting. Lacquer is very monolithic and dissolvable by its own solvent after it dries. In this case yes, I believe you are correct.


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## PACman (Oct 24, 2014)

NACE said:


> thermoplastic coating vs thermo setting. Lacquer is very monolithic and dissolvable by its own solvent after it dries. In this case yes, I believe you are correct.


I know it started as an acrylic thread, but like all others it wandered a bit. But back to the op I don't think I've ever seen two acrylic coats not cure because the first coat wasn't dry or cured. Otherwise you would have a long wait after your prime/first coat wouldn't you? You wouldn't want to wait 30 days for your bullseye 123 to cure all the way before you topcoated it.


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