RE: Varnish Problems

[danny efferson]

Hello Everyone,

In an effort to find a fix for my problem; I was browsing the web and happened to come across this forum. Everyone seems very knowledgeable.

Here's my problem I am building a house where I have alder cabinets. I stained them with Sherwin williams bright cherry then came back with SW sand and seal. SW recommended that I come back with Fast dry varnish so that is what I am trying to do, but it looks horrible. Where I live the humidity is high. This varnish is drying so fast that if I make a long stroke and try to brush out any sags it has gotten tacky and ripples. I am using a foam brush it even leaves marks.

I am going to sand this out and would like to know what I can use on top of this that will be a little easier to work with. I am not a pro painter just a humble diy. I have not applied the varnish to all of the cabinets so if I change will I have an uneven finish. What would you guys recommend? So that I could get a finish I am proud of?


Some of my thoughts are as follows: 1. I could continue to varnish the cabinets and have to sand them all and then cut the varnish with mineral spirits and apply the remaining coats with a rag. (but would it dry just as fast?) 2. I could sand what I have and switch to Cabot regular varnish (if possible and what would be the best method of applying). 3. I could lightly sand what I have and switch to Polyurethane (would it be possible to switch to a waterbased poly?)

It has been around 10 years since I finished cabinets and at that time I used BM waterbased poly.

Any advice or tips, recommendation would be greatly appreciated.

danny :confused:

[Anthony Whitesell]

What is the temperature of the area where you are doing the finish work?

IIRC, humidity will actually slow doing the curing, not speed it up. I could be wrong on that.

If I read you finishing plan correctly: first was Bright Cherry Stain, then sand and seal, then varnish. I think that order is incorrect. The sand and seal should be put on first to help with the finish sanding and sealing the wood pores so the stain will go on evenly and not be blotchy when dried. Most sanding sealers have lubricants in them to help with the finish sanding and should be covered by the stain. Because the order is reversed that may be playing into the problems with applying the varnish.

Are you brushing the varnish on straight from the can (ie., full strength, you haven't poured some out and thinned it)?

I would mixed up some thinned 10-25% with paint thinner and brush it on (not wipe/rag). I've been told that Paint Thinner has mineral spirits and other chemicals that will result in a slow evaporation rate. I'd look for some non-100% Mineral Spirits Paint Thinner for the thinning based on your situation. The thinning may also help with the sags.

Foam brushes will work but only until they get saturated. Once they are saturated with varnish they will not allow the air out of the varnish while on the brush and you will be adding air bubbles to the finish, so be prepared to use a few foam brushes or switch to a bristled varnish brush. When using a brush, don't forget to "wet" the brush in the "solvent" before starting (water for WB, paint thinner for varnish, DNA for shellac)

You've picked what has been listed as a good choice varnish. The Cabot Varnish is on the same list. I wouldn't go back to the poly. You'll just end up with more problems (same curing issues, but now you'll add the adhesion issues, etc.) Either way they both need to be thinned before applying.

[danny efferson]

Thanks for your reply. The temps here are in the 90 to upper 90's, humidy at 94%. I would think that the humidty would have slowed down the drying, but it is drying fast.

Maybe my problem was not switching the foam brush and it was going on to thick (causing the sag in the first place). I will sand, thin and try again. I think I will start with a fresh can also. When I used the brush it was leaving brush marks bad; that is why I switched to the foam brush. I was expecting them to level out, but that did not happen.

I followed the instruction of Sherwin Williams, stain, sand and seal then varnish.


Thanks a million,

[Steve Schoene]

From this point, I would stop for a day or two, then sand the varnish that has given you problems smooth, being sure not to cut through the stain. You will have removed enough that I strongly doubt you will see any color difference it you top coat with a different varnish, and if you do find that area is noticeably darker, you can get even closer with an extra coat of the new varnish on the lighter areas.

You didn't mention thinning the varnish. All oil based varnishes must be thinned before using. The manufacturers lie about that since if they told you you had to thin the varnish, they might have to include that additional thinner as part of the VOC content in the varnish. You may find that thinning the SW FastDry varnish 10% - 15% using mineral spirits, not naphtha, will give you enough time. Discover this on a sample board, prepared the same as the cabinets, not on the cabinets. It's not the humidity that is the problem, it is the heat. The solvent evaporates much faster in warm temps. More humidity slows the evaporation but only to a small degree compared to the effect of temperature. Any varnish, and particularly the FastDry, will set up too fast with temps in the 90's. Find a cooler place to work. (You aren't attempting to do the doors in place I hope. They should be removed and varnished flat in any event.)

I strongly recommend you give up the foam brush. They can introduce bubbles, and don't spread out the varnish very evenly, or do a good job of tipping off. A good natural bristle brush will make the problem easier. Here are some good ones as examples.

http://www.homesteadfinishing.com/htdocs/Brushes.htm

You can also likely find a decent Purdy at your S&W store. I really like the ones with some ox hair mixed in, but a good china bristle, with a chisel tip, not cut flat across should work. But, buy the top of the line, not the "contractor grade".

Now, for next time, lose the sanding sealer. If you needed a wash coat to keep the stain from "blotching" shellac would be best, and even heavily thinned varnish would be better. Now Seal Coat, by Zinsser, is labeled as if it were a sanding sealer. It isn't, it is just dewaxed shellac, and is OK.

The Cabot Varnish (not their Polyurethane) is a good varnish, similar to McCloskey Heirloom that it is replacing. Another very similar varnish is Pratt & Lambert 38. These are a little lighter in color than the FastDry, but one coat over stain will make little difference. Waterlox makes good varnish that is a bit darker. The Original/Sealer is thinned for use as a wiping varnish. It is a semi-gloss that would look nice if you like that shiny. They also make a Satin, which is thick enough to be brushed without much extra thinning and could use a dollop of thinner to be wiped on.

I would NOT shift to an oil based polyurethane varnish. It will have significant problems adhereing to sanding sealer, and won't look as nice anyway. The only advantage polyurethane varnish has is abrasion resistance, not an issue with cabinets. Waterborne finish may also have problems adhering to sanding sealer. While generally durable enough, the waterborne will be not nearly as bullet proof, especially with respect to chemicals, as an oil bsed varnish. You could finesse the problem by applying a coat or two of DEWAXED shellac over the sanding sealer before using either oil-based polyurethane or waterborne (acrylic) polyurethane.

[Prashun Patel]

I agree (humbly) with Steve.
In my short time working with oil varnish, I've found you can get professional results by thinning up to 50% with mineral spirits and wither wiping on or using a great quality china bristle brush (I use purdy to good effect).

My current favorite schedule is to wipe on the first 2 coats thinned at 50%, then brush a coat or 2 at 50% then another coat at 25% and then wipe on 2 more coats at 25%. Knock down nubs in between with > 320 gt. It builds well and requires very little sanding. The wiping on of the first few coats fills up the pores so the subsequent brush coats slide nice and slick.

[danny efferson]

Thanks for the reply. I did not thin prior to application. I started out using a Purdy 100% natural white china brush 2 1/2 inch. I did purchase this one at Home Depot. I couldn't tell if it was contractors grade or not. I will go to SW see if I can find one with a mix of ox hair. I have a lot of cabinets so I will lose the foam (it will take way to many). It has been a couple of days since I touched the cabinets. I will go sand them this afternoon and reapply thinned varnish tommorrow. I have several scraps that I will practice on prior to touching the cabinets.

I haven't started the doors. just the face frames, but when it was going bad I stopped. No sense making more work for my self.

You guys have been a big help. I think my error was foam brushes, not thinning, and painting straight from can ( this probably thickened the unthinned varnish and shortened the dry time).

I'll start with a new can thinned in a separate container. unfortunately, I can't do any thing about the heat. Predicted temp today 90 degrees and it's cloudy and raining.

Thanks,
Dan