Advice on Conversion Varnish

      A beginner gets tips on product choices, application techniques, and conditioning the workspace. March 18, 2005

Question
I'm a small cabinetmaker and finisher in Washington state. I'm finally switching over to conversion varnish. I have chosen to go with Sherwin Williams dull rubbed CV, with a vinyl sealer under it. I have a small amount of knowledge about CV, and SW CV in particular, as I worked in the finish room of a shop before I started my own company a couple of years ago. But that was a while ago and I was more of a stainer and sander at the time.

1) I use an airless for spraying. What tip works best for CV?

2) I remember there being some problems between the vinyl sealer and CV when I was at that shop - have they worked that out? I've read how important it is to sandwich glazes and such between vinyl sealer that I feel I need to use it. Do you?

3) I've read there are different catalysts - which one do I need to use? (The SW store where I am getting my CV does not carry industrial coatings and are just doing so for me - we are way out in the sticks!)

3) Does the vinyl sealer need to be catalyzed? And is catalyzed vinyl sealer a different product from regular vinyl sealer or just the regular with catalyst thrown in?

4) Are you who are using airless sprayers spraying right out of the can, or are you thinning it and if so, how much (Xylene or High Flash Naptha, right?)?

5) I worry a little bit about the temperature we are able to obtain in the shop, as we are such a cold region during the winter and I don't have the money for a heat make up unit. Anybody fess up to spraying it in a little colder room than it recommends and not having problems?

Forum Responses
(Finishing Forum)
From contributor R:
If you can't keep the product above 68 degrees for spraying and 48 hours after for curing, I recommend that you don't use CV. It will shatter like a bad piece of glass in a few months.



From contributor D:
I absolutely do not recommend using vinyl sealer under S-W conversion varnish. I've never had success using it even when properly catalyzed. Use the C-V as a self sealing system. It sands better than vinyl sealer, so why use vinyl sealer?

Contributor R is right about temperature. C-V loves heat. If you try to spray this stuff below 50F, you're dead meat. C-V is a superior finish, but it is unforgiving.

Lastly, Global Resistovar by Valspar is much better than the SW CV. I also can buy it a lot cheaper. Go this way if possible.



From contributor G:
I don't use an airless system for my clear finishes. I use an HVLP setup with a 2 1/2 pressure pot. So I cannot help you with that. I have sprayed clears in the past with one and found it to be a lot of trouble cleaning.

First, Sherwin Williams vinyl sealer can be used both catalyzed and uncatalyzed. It is the same product. There are a couple of benefits when you catalyze it: 1. you get greater moisture resistance and 2. you get higher, faster build.

I do recommend sealing varying color coats with vinyl sealer. I often seal my first coat of stain with vinyl sealer and to boost the color, I often shade with the same stain and seal that color coat with another coat of vinyl.

I have used both in cold weather with only one adverse affect. The vinyl sealer sometimes does not sand without gumming the paper and I find that I have to rub all the sanded surfaces with synthetic steel wool.

Back to the airless setup. You probably can push the material through without thinning. But I would probably use a fine finish setup for better atomization and therefore would probably thin within the 15-25% recommended.



From contributor B:
Things have changed since you last used the product. I would call your SW rep and get a product catalog and a MSDS on each product that you plan to use. You will get many answers to the question of if you have to catalyze the sealer and what catalyst to use (V66V21). Have a tape recorder hooked up to the phone and ask many questions; call back the next day and ask the same questions and compare the answers. As it stands, most reps at Sherwin Williams wouldn't know what day of the week it was unless you pointed it out to them on the sports page, and the ones who did would most likely claim that the sports page was a day old.


From contributor J:
Keep your material off the cement and close to the high 60's. Also watch the moisture content of your woods and temp of the shop. Fluctuations in temp and humidity will doom any finish well before it is applied to the wood because of this. CV is like marriage - when it's going good, it's heaven and you're on top of the world. If you're not paying attention and doing all the right things, you will find yourself at the gates of hell!

I've never had a problem with vinyl sealer. I use the T67F3 24% solids and this is catalyzed with v66v26. The other catalyst is for the topcoat v84v83DRE and is catalyzed with v66v21. If topcoat catalyst is used in vinyl sealer, you will shorten an already small for catalyzation effectiveness and then you will have finish failure. Leftover catalyzed finish can be saved by either adding same amount of uncatalyzed finish and catalyzing for the amount added new the next day, or you can put it in the refrigerator (slows down the catalyst reaction).

I know I just got done telling you to keep CV room temp. This still holds true and you must bring cold CV back up to room temp. This is going to make people cringe, but here goes: I use those space heaters, the ones that kick out 350.000 btu of heat! After spraying each coat (I double coat for build), I cook CV off after fan has removed enough fumes and heat doesn't escape out booth. I kick on spray booth to vent occasionally. This sets CV up quick and allows me to speed up process and limit junk falling into finish.

Also, keep the finish department immaculate - you will find out just how clean I mean - and mist ground and door jambs to keep any dust from kicking up while spraying. I use an airless with a whip end for ease of wrist motion, Reverse-a-tip on a contractor gun. This gives you a filter at the pump and one in the gun, and I also put one on the intake hose (nylons/pantyhose). Your tips should range from everyday use 413 down to a 310 for narrow areas. The tips are fine finish rac 5, I believe (they're green as opposed to black or yellow).



From contributor T:
I am a dealer in Oregon that sells 5 different manufacturers' lacquers. I find that Chemcraft has the best glaze, vinyl washcoat, reactive amino topcoat systems, etc. of our manufacturers.

I think that Rodda Paint is the distributor in WA. They have a rep that strictly calls on small cab shops like yours. You may want to contact them or log on to Chemcraft's website and look for a local distributor. Whatever you decide, find a distributor that knows the product line. I was greatly concerned when you mentioned in your post that your local SW doesn't carry industrial coatings and were doing you a favor. Misinformation or lack of info and product is not a favor.



From contributor J:
Don't you mean to say RUDD coatings out of Washington? Bar none they had the best pre-cat lacquer before the V.O.C. limits took their toll. That stuff could take quite a few soaked wipes with lacquer thinner before it would start to remelt. Then I made money!


From contributor T:
No, I sell Rudd too. We sell about 10 to 1 more Chemcraft now, whereas 3 years ago Rudd was our lead line. Chemcraft has stepped up in our need for glazes, crackles, and specialty finishes. We are even doing hands on classes for end users with Chemcraft annually. Chemcraft also seems to have a better environmental stance too. Most of their products are 0.00 HAPS and VOC are all under 550 GPL and some are under 350 GPL.

Rudd came out last year with Duracat V (withstands 40 MEK rubs), but most of our users still prefer the ease of application and superior durability of the Chemcraft. After all, how many people rub their cabinets with MEK or lacquer thinner more than the KCMA standard... Rudd still has its good points, though, and we do like most of their products. Rudd being in Seattle is a great benefit because they are much closer to us from a shipping standpoint. If there is a Rudd distributor near the questioner, I wouldn't hesitate to call them either.



From contributor M:
SW conversion varnish is good for table tops. If you find particles in the cured finish, try switching your paint filters to Gerson 2000. This has left my large (5'x12') conference tables flawless.


The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor F:
I would like to add a note about Rudd Duracat. The product is very hard, but it is important to know that there is a recoat window of 4 hours, after which the next coat will not adhere to itself unless you scuff it. The product is very brittle and is prone to peel up if scraped by the fingernail. We had an oven cabinet that had to come out and be refinished as it was peeling badly. I'm guessing this was due to waiting past the window and or not sanding before recoating. Not fun.

Recently we have been having some interlayer separation (peeling up of the finish layer when blue tape is removed, during scribing, etc.) and after much experimentation and considering of the various variables we have concluded that our problems began when we started to use wiping stain concentrates in place of glazes. We typically stain/lacquer for a barrier coat then glaze, then add 2-3 coats of lacquer. We believe that the stain concentrates do not have the right properties to adhere the lacquer coats below and above when used in place of true glazes.

We have now switched to the Valspar system and we are using their glazes and pre-cat lacquer. By the way, in preliminary testing, their conversion lacquer is incredibly tough and we plan on using it on our bar tops and tables. The thumbnail test fails completely to scrape up the lacquer. This is the only one I've tested this way that passes this test. Their pre-cat is silky smooth and our finisher likes working with it.



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