2K Poly Versus Conversion Varnish
Comparing two-component polyurethane with converersion varnish on practical terms. April 15, 2012
Question
Regarding 2K poly - what precautions are needed for health and how expensive is it? What's the drying time compared to CV? Can you use it over glazes? Any special equipment needed? How does it compare to durability with CV? Can I get different sheens? An advice is appreciated.
Forum Responses
(Finishing Forum)
From contributor B:
No different than if you were spraying CV. It’s twice as expensive as CV, but twice as good. Some dry quite a bit faster than CV, some are slower. Yes, but test your finishing system to ensure good inter-coat adhesion before committing to or starting any job, not all glazes are created equal. No, just make sure you don't leave material in your equipment very long, they have a short pot life. Most 2K's outperform CV in every way.
I can't speak for everyone, but the stuff I use from Gemini (they are making their own now) had four sheens (90, 60, 30, 10). There are several great manufacturers of 2K's, whomever you use, follow their instructions and recommendations. Once you get to using the products, they are no harder to apply than CV.
From the original questioner:
Another question, is there a sealer for first coat? Or do you just self-seal? How many coats of 2k? I normally use S/W fast dry vinyl sealer as a first coat to minimize chances of contamination.
From contributor B:
There are sealers, most are reduced versions of the topcoat, some are formulated to be sealers. If you are refinishing, using oil stains or glazes, you absolutely have to use a barrier coat, AKA Isolante. This very thin coating prevents oils from contaminating the polyurethane and causing delamination. This is especially important when using exotic woods (ipe, teak, etc.). The manufacturer (or their sound distributor) should be able to set you up with the recommended system depending upon your application.
From the original questioner:
To contributor B: sounds like you know about the 2k material, and I've thought of a few more questions: Is it non yellowing? Is it available pigmented? If not, how do you get painted products? If I average about five gallons of product for a kitchen at about $150, and the 2k is twice that much. That means I get a much better product for an extra $150. So why isn't everyone using this product?
From contributor B:
Yes, non-yellowing. Some are, some offer their clears that you can tint up to 20 ounces of pigment per gallon (that's nearly twice as much as CV). I would check with the various manufacturers and see what they offer. All of them make good stuff, there's just some that are better than others. Some don't use it because it costs a great deal more. Others don't use it because they are not familiar with the technology (you know we are all creatures of habit).
From the original questioner:
Other than expense, any disadvantages at all?
From contributor B:
Short pot life (some are four hours). Some dry slower than others (some are four hours dry, but that's not really a bad thing). They may not hang as well, although they could be lower in viscosity, the volume solids is much higher in many cases and care should be taken when spraying vertically. They are moisture sensitive, especially the catalysts and accelerators, take care to keep them sealed at all times. Stick with the thinners sold by the mfg. They have a low moisture content.
From the original questioner:
I get what you mean by moisture sensitive, but what are the results of moisture sensitive?
From contributor C:
I use ILVA products. They have an acrylic urethane which is very clear. Their standard 2K urethane has a slight amber tint. The sealer is about 40% solids whereas the acrylic topcoat is only 23%. I use a supplied air mask. Once dry there is no lingering smell like CV has.
From contributor B:
Moisture can cause drying and cure problems. While the film may appear to be dry, there could be soft spots, some areas that are shiny, might even have a wrinkle.
From the original questioner:
"Moisture can cause drying and cure problems. While the film may appear to be dry, there could be soft spots, some areas that are shiny, might even have a wrinkle." How is this prevented?
From contributor B:
Use the solvents the manufacturer recommends, and keep the lids tight on your containers. Also be mindful of your air compressor and lines to ensure your moisture traps are working.
