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Can G-F Hi-Perf Water-Based Top Coat Be Diluted Into A Wiping Varnish?

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Forum topic by gargey posted 06-02-2016 05:42 PM 970 views 0 times favorited 14 replies Add to Favorites Watch
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gargey

483 posts in 241 days


06-02-2016 05:42 PM

Hi Guys,

Can General Finishes, Water Based, High Performance Top Coat be diluted with mineral spirits to create a wiping varnish?

Or does diluting with mineral spirits only work for oil-based products?

...

Separately, since it is water based, does it have less of a yellowing effect compared to “regular” (oil based)polyurethanes?

I know it is a polyurethane, so there may be some yellowing from that compound, but if I understand correctly much of the yellowing from “regular” polyurethanes comes from the oil base.

...

I’m a complete novice at finishing. I’ve read a few of the articles from Fine Woodworking that describe wiping varnish, but it’s tough to keep it all straight.

...

While I’m at it, what should or should not be used under or over water based topcoats? Are there any rules of thumb? I know some people put BLO and then oil topcaots, not sure if you can do this with a water-based topcoat.

Thanks


14 replies so far

View bbasiaga's profile

bbasiaga

757 posts in 1461 days


#1 posted 06-02-2016 06:02 PM

Oil and water don’t mix. If you need to dilute the water based poly, do so with water.

In general the water based poly will yellow less than oil based, but it isn’t perfectly clear (still a slight yellow hue).

The can will tell you what finishes are compatible. I have heard of a lot of people using shellac under water based poly. I have even heard of danish oil. Both have to be allowed to COMPLETELY dry to avoid cracking the water based tip coat. Dry for 7 to 10 days seems to be the most common advice. I haven’t tried either of these myself though.

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View Bill White's profile

Bill White

4456 posts in 3426 days


#2 posted 06-02-2016 06:39 PM

Believe what was posted by bbasiaga.
Bill

-- bill@magraphics.us

View Fred Hargis's profile

Fred Hargis

3945 posts in 1959 days


#3 posted 06-02-2016 06:56 PM

Some things to consider: It’s not “polyurethane”, waterborne finishes are mostly acrylic resin formulas. The friggin magic word “polyurethane” has some of them adding a small dollop of urethane just so they can put the damned word on the label. Finish chemistry seems to be advancing rapidly, and there are some “oil modified waterborne finishes” that may have more of the urethane resin in them.

As for the “yellowing”, it’s as you said. That’s actually from the linseed oil in most oil based finishes, though I suppose a very small part of it could be from the resin. Don’t forget, most woods will also turn darker (for light woods that might be a “yellow”) over time. Dark woods generally get lighter, though. You can get an oil based varnish that has a lot less of the amber cast, but it has to be made with soya oil in place of the linseed oil (Pratt and Lambert 38 is the only one I know of, very hard to find).

Most waterborne finishes can only be diluted a little (check the label…the most I’ve seen was 20%, and a lot of them are less) and going past that threatens to screw up the chemistry. The water is only there to keep the finish molecules separated during storage and application, it then evaporates to allow those molecules to “coalesce” into a film finish.
You can put BLO under a waterborne, though that will add to any yellowing over time. As said above, it must be fairly cured for this to work, I wait a week. Shellac isn’t a problem at all, as long as it is dewaxed. Waxy shellac might work under some of the waterborne formulas, but it’s a gamble.

I suggest you get Bob Flexner's book and read it. very easy to follow and good reading, it has a huge amount of useful info on finishing. Jeff Jewit also has one with pretty much the same info and is just as good. One or both should be required material in any hobbyist woodshop, IMHO.

-- Our village hasn't lost it's idiot, he was elected to congress.

View gargey's profile

gargey

483 posts in 241 days


#4 posted 06-02-2016 07:32 PM

Fred,

When I bought the can I thought it would be acrylic, but went to the website and the General Finishes adds “Polyurethane” right into the name of the product (it’s not on the can).

See here: https://generalfinishes.com/retail-products/water-based-top-coats-sanding-sealers/ef-high-performance-polyurethane-water-based-t#.V1CJRXIUWM8

Thanks for the other info.

View Fred Hargis's profile

Fred Hargis

3945 posts in 1959 days


#5 posted 06-02-2016 08:30 PM

From the GF High Performance technical data sheet:
Classification:
Water Based Urethane / Acrylic Finish
Product Description:
High Performance Poly is a unique Hybrid of urethane and acrylic technology.

Not spelled out is how much urethane is in there; but none of them provide that.

Lest I be misunderstood: I love GF HP, as well as Endurovar ( a modified oil product, I think)...what I don’t like is the misleading BS doled out by the manufacturers.

-- Our village hasn't lost it's idiot, he was elected to congress.

View OSU55's profile

OSU55

1062 posts in 1455 days


#6 posted 06-02-2016 09:25 PM

We don’t know if the WB poly’s have a little or a lot of urethane in them, but the abrasion and chemical tests I’ve been able to find do show the WB poly’s with a distinct advantage over the non-poly WB finishes.

As for yellowing, it depends on the WB product. I use Target EM9000, and it is water clear when cured.

Each mfr will have a max dilution for their product, and it is with water not MS. Target, GF, and some others sell a retarder that helps with hand application. Most will recommend a foam brush. WB finishes are best sprayed, though.

Both of these books are worth having: Great Wood Finishes Jeff Jewitt Taunton Press 2000 Understanding Wood Finishing Bob Flexner Reader’s Digest 2005

WB finishes can be used over oil based stains or Danish oils etc. They need to be dry, and wiping them with 1:1 DNA/water can help ensure good adhesion.

I use dewaxed shellac often under WB finishes. I mix transtint dyes directly in 1# cut and less shellac to use as a toner. WB finishes can lift WB dyes or stains, and a light coat of shellac will prevent this. Also, WB finishes can appear lifeless – shellac provides a lot of chatoyance that is lost with WB.

View gargey's profile

gargey

483 posts in 241 days


#7 posted 06-02-2016 10:28 PM

That’s very helpful, thank you.

Hopefully I can find de-waxed shellac at Rockler or Home Depot, I’d like to try your suggestion. Also hopefully it’s not something I have to spray. I’m very ignorant about this stuff at this point.

View OSU55's profile

OSU55

1062 posts in 1455 days


#8 posted 06-03-2016 11:55 AM

Excellent article by Jeff Jewitt on shellac. He has some other articles on his site you find interesting. I get shellac flakes from Shellac Shack. I use DNA from the bbs to dissolve/dilute.

View bbasiaga's profile

bbasiaga

757 posts in 1461 days


#9 posted 06-03-2016 12:01 PM

Home Depot carries the Zinsser dewaxed shellac. It’s sold as a sealer or something. Gallon can only, clearly says dewaxed on it. The smaller cans that are yellow or orange are not dewaxed.

Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View ScottM's profile

ScottM

346 posts in 1612 days


#10 posted 06-03-2016 12:30 PM

Both HD and Lowes, at least around here, carry the dewaxed Shellac in the rattle can. I used it just recently on a project under EM6000 lacquer. Excellent finish.

View upinflames's profile

upinflames

209 posts in 1628 days


#11 posted 06-03-2016 12:37 PM

A+ on the article by Jewitt, lots of good info on the shellac shack site also. Just a quick FYI, If you pick up the gallon can of Zinsser as soon as you can transfer it into quart or pint glass canning jars. Place it in a cool dark place and it will last much longer, not to mention some folks have had the can spring a leak and make a nice little mess.

View CharlesA's profile

CharlesA

3024 posts in 1263 days


#12 posted 06-03-2016 12:53 PM

Zinsser Sealcoat works just fine. Dewaxed shallac dries fast and the GF HP goes nicely right over it.

I may not be an expert in many ww things, but I am a bit of an expert on how to screw up GF HP application. Don’t use a regular brush and don’t try to wipe on with a cloth. If you’re doing a small surface, then the foam brushes work well.

But if you’re doing a top the siize of a desk or larger, brushing becomes less satisfactory, Especially as the temperature gets higher (ambient), brushing over large surfaces can produce lines and irregularity. Thinning with their thinner or water (20% max is right, I believe) may help, but there are two techniques that work best:

1. Second best: use a paint pad applicator(see GF website) and cover it with a woman’s footie hose (for real). Use continuous strokes the entire length of the surface. In 90°+ temps last summer on a larger desktop I could never get even this technique to work well.
2. Best: As noted above, it is a joy to spray GF WB. Had I not started spraying it, I might have given up.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

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gargey

483 posts in 241 days


#13 posted 06-06-2016 01:42 PM



Both HD and Lowes, at least around here, carry the dewaxed Shellac in the rattle can. I used it just recently on a project under EM6000 lacquer. Excellent finish.

- ScottM

You just spray it on and leave it? Or should you rub it in too?

Thanks

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ScottM

346 posts in 1612 days


#14 posted 06-06-2016 02:53 PM

Spray a coat of dewaxed shellac from a rattle can, let it dry and then a light scuff sand with 320. Then you can apply any finish you want over that. The shellac acts as a sealer. The EM6000, according to the can directions, can be sprayed or brushed/wiped. However, you should only brush it on small parts due to the fast dry time.

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