Pigmented conversion varnish
Finishers help troubleshoot problems with drying, overspray and more. January 21, 2002
Question
I always wanted to stay away from CV because of possible problems with application and temperature (cold), but I needed a harder finish that would not yellow--hence, pigmented CV. We got around the issue of CV (when demand for pigmented finishes was minimal) by using pigmented vinyl sealers, then either clear pre-cat over dark colors or clear CAB acrylic (not catalyzed) over whites. Finish looked great, but repairs to scratches through the color did not blend well. We switched to a pigmented CV. First two coats catalyzed primer surface CV--amazing stuff--then one or two coats pigmented CV. The pigmented CV sprays great and looks great. I was surprised to see how long we could spray inside and out with absolutely no over-spray--seemed to keep melting in. We are having a problem, though. (We are on the East Coast with plenty of humidity and spray with HVLP in a certified booth.)
- Even after measuring the coats at 3 ml wet, we still can’t sand the same day to apply more than one coat a day.
- We spray doors and door fronts way up on stilts and the CV still attacks the underside if it has been previously coated (even the day before) with CV.
- Print resistance is terrible even after a full 24 hour period, so doors/drawer fronts will show stilt marks.
- Supplier said most other shops do not shoot a clear scuff coat over the pigmented coats. It is a matter of preference. Is it? I wanted to believe him, but the coating does not seen tough enough.
- Field repairs are impossible, so damaged pieces have to be totally re-coated in the shop.
So what’s the deal? Someone I know shoots CV and says it was designed to be oven-dried, not air-dried. Is this true? I will not go back to pigmented vinyl, and I will not get an oven. What about pigmented catalyzed production lacquers or pigmented pre-cats? What is the system that would fit the small shop? We presently use all Sherwin Williams products and would like to keep it that way.
Forum Responses
I worked for many years for a coatings supplier. We had many different catalysts for the CV materials. Some of the hotter catalysts allowed the coating to surface dry in a very short time but total cure took several days. Repair was difficult especially when re-coating because of lifting after re-coating. Some coating suppliers say their CV is re-coatable but you will have to see this for yourself. Most of the large companies make very good CV coatings but you will have to adapt each one to your needs.
From contributor D:
I've used the Sherwin-Williams WW CV for years and the stuff has always dried great for me with three coats a day being no issue. But I live in Arizona. Make sure you're using the right catalyst. SW makes two. One for their vinyl sealer, which is quite mild, and one for the CV, which is a lot hotter. The catalyst you should be using with C-V is V66 V 21, computer number 5010-03560.
From the original questioner:
We are using the correct catalyst. Did you usually leave the pigmented CV as your final coat or did you find the need for a final clear CV scuff coat to further protect the finish? Also, did you have any problems with spraying one side of a door, drawer front, or panel on the turntable and having the underside get affected by the slight over-spray, leaving a gritty feel?
I gave up on CV and pigmented lacquers. Try using a good enamel. Sherwin Williams, Benjamin Moore, etc. The key is to thin the heck out of it, with lots of naptha and maybe some spirits. The thinner the better. You should be able to get in two coats in a day. No catalyst, no pot life, no funny finish problems. More important, it looks great and is easy to repair. If you're installing your own built-ins, touch up blends well. The only catch is that if you want a satin sheen, you'll want to use equal parts semi- and high-gloss. The naptha tends to dull the sheen a bit.
From contributor D:
CV is much slower drying than lacquer and the reason why the over-spray can attach itself to the unmasked area. That's one of the reasons we love it here in hot Arizona. In the summer, if we try to use lacquer, we end up spraying sand. In the winter, I use pre-cat and in the summer CV. The slower dry of the CV in summer is a benefit and the
quicker dry of the pre-cat is likewise a benefit in the winter.
The pigmented CV is the same product as the clear, only with HULS 844 colorants added to it. I can't see any benefit to topcoating it with clear unless you're trying to adjust sheen. Try out ML Campbell's Duravar. This is a very highly regarded product.
I was using one product, then another and wasn't getting what I wanted. I required pigmented colors, also. I used pre-cat lacquer, with a clear coat for sheen adjustment and protection. I used CV for a while. Then back to Magnalac. I was concerned about the cracking of Magnalac.
Then after a while it finally soaked in. Use a primer to get your build up and protection and smoothness. Build it up even if it takes 2-3 applications. Sand smooth and apply no more than 5 mil dft. of pigmented Magnalac. The application here is the key. If you have a good spray head utilizing the correct air and fluid input for the product and if you need to have an additive such as Flow enhancer#2 or something like MAK to slow it down, then use it.
Star had a product for the over-spray that you described. It is added to the lacquer about 2-3 oz per gallon. You mentioned using stilts. This indicates that your product is too high in spraying mode. As you spray the top portion on the edges, the over-spray wraps around underneath. Lower your stilts and spray at an angle on the edges, without going underneath. But with the additive in your spray product, even if the overspray goes under, it will stay wetter long enough to blend in without drying out.
Sometimes the reducer/thinner is not the recommended product for the lacquer being used. Some reducers are classified as fast, slow and medium. Use the one for the temperature recommended. If it's cold, use the fast drying one. If it's hot, use the slow drying one.
I like CV, but had a problem with acquiring the tinted product here (plus a couple of other problems). The Magnalac (ML Campbell) product may not be available to you, but any good pre-cat will do. The final product to be used is determined by what it goes on and where it is to be used.
Why overkill? However, using one product for everything is also advantageous. Even more so if it is straight white, not tinted. But I think the application procedures could be adjusted somewhat and you could see some improvement.
Whoever told you that CVs are made for ovens is trying to sell an oven.
Wherever you are spraying CVs, post catalyzed or pre-cat lacquers, or even one-component water-based topcoats, if you don't cover the undersides of your doors with either paper, cardboard or wood planks of some sort, you will get over-spray.
Also, using a CV primer is a good idea because it fills better, dries faster, and sands better. But you should still be able to spray 2-3 separate coats a day with a CV topcoat, even using it as a primer. Use a fast thinner for the primer and always use a slower thinner with topcoats. See if your thinner might be an actual retarder. CVs are always recommended over lacquers for non-yellowing characteristics. They might dry a little bit slower, but they more often than not are higher in solids, therefore you don't have to put on as many mils to achieve the same quality finish.
As far as clearcoating over your pigments, it acts as a sheen adjuster and when cleaning, it helps that you are rubbing on a clearcoat versus a pigmented, or better, a white. But you do not have to do it at all. Besides, it is an added throughput cost. Overall, no matter what you choose as a finish, or where you finish, follow product protocol.
From contributor R:
The cold temperature of your shop is the problem, I believe. Is there some way to heat your shop to at least 68-70 degrees? I use Magnalac pre-catalyzed lacquer for my pigmented projects, especially when touch-up will be required. I also use a drying rack for
cabinet doors and drawer fronts (picture below). On average quality jobs (rush) I spray the faces last and then just rub out the backs with flat-lube.
On a job that has to be perfect, I spray the back, wait overnight, then mask-off the back and spray the front and edges. I don't even stain both sides at once. I stain the face and edges, let dry seal just the face (no edge), flip it over, sand off any runs, drips or overspray marks that I may see and stain the back. I then check the edge to make sure I didn't get any runs, drips or errors and seal the back and edges. Using the drying rack, if I put a door in with wet stain, it will have rack marks when the stain dries. This may seem like a lot of work, but when you get used to it, you can do a huge amount of doors or drawer fronts a day.
I have used CVs for many years off and on. They are a heck of a lot better now than they used to be in terms of flow, cure, etc. Ovens are ideal for curing these products, and most certainly recommended by the suppliers. But since you don't have one, you have to expect a slower drying curve, since it's the heat that jumpstarts the polymerization. Nonetheless, it should not take as long to cure as you are indicating. If your solvents, catalysts, etc. are right, as they seem to be, I have to agree that your plant conditions are the primary culprit. If you are drying in the open, you need to get at least some dry heat going and air movement if even from a portable unit.
From the original questioner:
We actually started shooting pigmented conversion varnish four months ago. The temperature problem was not originally a factor. We even super-heated the spray room by firing up a kerosene torpedo heater (in August) in our staging room that is connected by a doorway. There is no way that room was not hot enough. Funny thing, one of the colors dried as slow as an enamel. All colors went from antique white to designer white (pretty light) and were custom mixed for us at Sherwin Williams. At the low level of pigmentation these whites required, it seems to me all of the batches should perform the same, no?
Someone mentioned the possibility of us not using the right thinner. We used SW K120. They said it could be used for the CV products.
From contributor D:
Wrong thinner. For CV, the thinners of choice are Xylene or Tolulene. Xylene performing better in my experience. K120 is lacquer thinner.
From contributor R:
Hi-Flash naptha is another option for thinning SW CV. It might help in your situation. Also, just because SW tinted your varnish doesn't mean that someone there didn't exceed the amount of pigment that you can use. Paint stores have done that to me. (And off-whites can be difficult to tint if you use too much of the secondary color--it's real easy to try and "fix" it by adding much more white. It doesn't take much of this to exceed 4 oz. per gallon of tint.)
Have you tried un-tinted CV? Does it cure slowly as well? If it cures okay, it may be the pigment levels as suggested.
R7K120 is absolutely the wrong stuff to use with Kemvar, and is almost certainly causing your problem. The correct reducers are the aromatics; Toluene is the quickest to flash off, followed by Xylene and High-Flash Naptha (not VM&P Naptha). I'd have a talk with the SW guys who advised you, and get your hands on SW's Chemical Coatings manual; there's lots of good info in it. Also, you might try using a pigmented catalyzed vinyl basecoat, followed by a CV topcoat, but find a Chemical Coatings rep who knows his company's products. A final thought: Are the SW guys using the correct (844) pigments for the CV?
844 or 866 will work fine. 896 will be a major problem as this is for waterborne finishes and contains glycol ethers which will dramatically slow the drying of the C-V. The above post might be on to the root cause of your problem.
From the original questioner:
I will run a test this week using the recommended thinners for conversion varnish. I do have a copy of the SW industrial coatings guide, and did see the recommended thinners for CV. Maybe it was my fault for asking the sales guy if it was ok if I used the R7K120 thinner. It gets to be so crazy between all the different coating systems (we have been through Hi-bild, opex, CAB, pre-cat, post-cat, wiping stains, dye stains, vinyls, pigmented vinyls, and now conversion varnishes).
I use a drying rack similar to the one in the picture, except I added shelves (1/2"x10"x16") with 11/4" drywall screws placed evenly throughout the board, allowing me to spray both sides at once, then set finished product face up in the drying rack to cure. Back side has 3/4" of air space to dry, with only the slightest evidence of screw tip prick.
From contributor R:
I don't like pin pricks even when they are slight. I find that by the time I go through the rack the first things I sprayed are dry enough to just flip 'em and spray again.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor M:
In most cases, SW does not "tint" any of the conversion varnishes. They are blended monochromatically. In other words they use package colors and weigh them out for tight, batch to batch consistency. The wait can be a while for some orders, but the product is a good one.
Comment from contributor A:
I have achieved great results with Sherwin Williams CV but they have recently changed their mix to the point of a 50/50 reduction. Even so, I can spray my coats and either flip the door to do the other side or even sand within less than an hour. I am just outside of Buffalo NY so I say keep the room temp at 60 to 75 for minimal issues. Also, touch-ups are no problem at all when it comes to blending. They call to use their catalyst as well but I have used standard lacquer thinner and have had no issues with drying or durability issues. I also use a turn table and have had issues with the reverse side having over-spray, so definitely mask the other side.
