Conversion Varnish over acrylic latex?

tiralie

tiralie

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Historically it was advised not to coat latex coatings with a conversion varnish. The advise was based on the fact that latex coatings are typically "softer" than conversion varnishes and over time my cause the CV top coat to craze or crack.

In the interests of my ongoing education, I was wondering if anyone can advise if there are issues coating newer water borne acrylic latex's, with a conversion varnish. I know finishers who do this, but always seal the acrylic latex with an Acrylic sealer.
Thanks
Tim
 
I've shot KA over painted hand rails, no issues to date. The base paint was SW Super Paint.

Tom
 
Tim Raleigh said:
Historically it was advised not to coat latex coatings with a conversion varnish. The advise was based on the fact that latex coatings are typically "softer" than conversion varnishes and over time my cause the CV top coat to craze or crack.

In the interests of my ongoing education, I was wondering if anyone can advise if there are issues coating newer water borne acrylic latex's, with a conversion varnish.
Thanks
Tim
Click to expand...

Tim,

I've been asked a few times over the years to do that and always declined. Partly due to mixed technology phobia.

I guess I've never fully understood the logic. The builders who have asked me to do it have believed that it would give the coating a harder surface and higher sheen.

My concerns are the same as yours, different levels of flexibility and potential long term incompatibility.

From a practical standpoint, if I build the latex finish, it seems backwards to then scuff it down and build a new sheen. The latex color isn't that coveted. I am more of the spirit to go to a different product altogether to achieve the goal.

What has your experience been?
 
i wonder if the advice to not put CV over latex has changed with the advent of water-bourne CV?
 
I'm doing some test pieces today with a latex paint color and then using Kem Aqua clear over the top.  I know its not CV but it's a system I'm interested in using when my color of choice isn't available in the Kem aqua blending white base.  From the sounds of it CV is the cats meow for furniture and cabinets, but being a home based shop there is no way i can or want to start using solvent based finishes in my garage shop.  So far I've been very happy with the KA clear over stains as well as the pigmented finishes for painted surfaces.
 
From my experience and current info it serves no purpose as the the finish is only as hard as the softest layer. Its a wasted step in both material and time. This is really evident when there is an incompatibility issue. Sort of like lipstick on a pig.

John
 
What about other factors besides harness...such as printing?  If it helped keep a surface cleaner (smudge free) then it may still serve a purpose in some instances?
 
kcufstoidi said:
From my experience and current info it serves no purpose as the the finish is only as hard as the softest layer. Its a wasted step in both material and time. This is really evident when there is an incompatibility issue. Sort of like lipstick on a pig.

John
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Agreed. I find that acrylic latex is too soft for my tastes so I have never gone down the route of adding a "protective" layer of either a conversion varnish or polyurethane.
Tim
 
Scott B. said:
What has your experience been?
Click to expand...

Well I have had no experience with it, hence my question.
Rather than have to spray 2 coats of acrylic latex and a conversion varnish for protection, why not just spray 2 coats of post cat lacquer and be done with it.
I have a preference for lacquer. I have reluctantly coated lacquer with Polyurethane, when I felt the surfaces might need extra protection but my experience has been that once fully cured, lacquer is very tough.

What I have read and been advised on by others, is putting a hard coating over a soft finish is not advisable. For instance in the kitchen renovation project I am currently completing I am painting some older cabinets and wanted to use some post catalyzed Agualente (lacquer) but the technician advised me that because it dries very hard, and it is impossible to tell what  the original cabinets were finished with, it would be better to forgo the post Catalyzed and just stick with pre-catalyzed.

My understanding is some cabinet re-finishers, will use a vinyl sealer or a 2K poly to seal the old finish and then follow up with their usual solvent based recipe. Water borne 2K poly is available, but I have not found a water borne vinyl sealer although my research indicates it does exist.

Tim
 
Kitchen cabinet manufacturers have used cv over latex for years with no issues. The key is using a flat paint vs. a semi gloss or gloss. It allows the sealer to bite in to the base coat. The flat paint dries hard and powders well when sanded. With the exception of pigmented lacquers and cvs, it is one of the nicest opaque finishes I've used. Touch up and rub out are also easier.
 
I do it on white railings, easier to clean and keep clean. I find it worth the few minutes it takes.

Why do the shoot clear over automotive paint? Durability and strength.

Tom
 
Tom the base/clear coatings for automotive that you refer to, are designed to work together as a 2 part system. The base used is not a stand alone product. There are coatings available for wood that are are also base/clear that are designed to work together. CV and latex were not designed to work together. Personally if you use it and it works go for it, just realize that there could be problems and should not be a recommended practice.

John
 
jhn_gdfry said:
Kitchen cabinet manufacturers have used cv over latex for years with no issues. The key is using a flat paint vs. a semi gloss or gloss. It allows the sealer to bite in to the base coat. The flat paint dries hard and powders well when sanded. With the exception of pigmented lacquers and cvs, it is one of the nicest opaque finishes I've used. Touch up and rub out are also easier.
Click to expand...
First time I hear about cabinet manufacturer to use latex
And then put CV over it
 
kcufstoidi said:
Tom the base/clear coatings for automotive that you refer to, are designed to work together as a 2 part system. The base used is not a stand alone product. There are coatings available for wood that are are also base/clear that are designed to work together. CV and latex were not designed to work together. Personally if you use it and it works go for it, just realize that there could be problems and should not be a recommended practice.

John
Click to expand...

I agree about the automotive products.

After 10 years without a failure and not being able to find a single manufactures document that says don't do it, I'm not to worried about the practice.

I don't by the rate of change argument, the latex has a higher stretch rate than CV or KA. We don't worry about failure of CV or KA when the base material moves seasonally. Either coating is only going to expand and contract as far as the base material moves.

Tom

 
BPCFinishing said:
I'm doing some test pieces today with a latex paint color and then using Kem Aqua clear over the top.  I know its not CV but it's a system I'm interested in using when my color of choice isn't available in the Kem aqua blending white base. 
Click to expand...

Tests and samples for color it makes sense to use what works. Kem Aqua is a lacquer and "softer" than Conversion varnish. I like it, it's very good. I have not used Kem Aqua+.
Part of the reason why I posted this question is that I ran into problems when I wanted to use lacquer but needed to match color requests from clients for small runs (
 
I'm only shooting KA because my store (don't get me wrong, love the people) didn't get it right.  I had to print off the PDS and bring them in just so they could figure out what I was talking about.  I'm about out of the KA so I'll be switching to KA+ after that.
 
kcufstoidi said:
From my experience and current info it serves no purpose as the the finish is only as hard as the softest layer.
John
Click to expand...

(I edited the quote for relevance)

Not true, some woods are softer than the finish. The finish really increases durability.

Tom
 
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