Wipe-on poly over Bullseye Amber shellac

[Jerry Brasch]

I'm building a craftsman style frame for a full length mirror for my sis. QSWO with minwax dark walnut stain followed by the Amber shellac and wipe-on poly top coat is a schedule that I have used many times without issue. I haven't found another combination that gives the ray fleck pop that old golden color like amber shellac. I know I can buy flake and mix my own but I'm not wanting to purchase 35 - 40 dollars worth of it right now. I know I'm not suppose to put poly over waxy shellac but I can't find out why. It seems to work just fine. So, I was curious if anyone else has had an issue with this. This is a birthday gift so I don't want it to disintegrate down the road.
Also, I have read where you can mix up a wiping varnish with poly, mineral spirits,and BLO. Was curious if that could give that golden color. Guess I should try a few samples, but would love to hear from someone who knows. I'm admittedly pretty green still. Thanks

[Scott Holmes]

Polyurethane varnish has trouble sticking to surfaces with wax. On a mirror it may have worked in the past and may work in the future. However it does not bond well and can easily scratch or scape off the shellac surface.

As for mixing your own wiping varnish your receipe is not correct. Equal parts of varnish mineral spirits and boiled linseed oil makes an oil/varnish blend a.k.a Danish oil, one sure brand name is Watco.

Wiping varnish is simply varnish thinned with mineral spirits.

The difference between the two is significant. Wiping varnish leaves a varnish finish no different than brushing on varnish albeit only about 1/3 the thickness.

Oil/varnish blends are "in-the-wood" finishes. You can't build a hard film finish with an oil/varish blend. To prove this students in my finishing classes, I show them a piece of glass where there is quarter sized spot of wiping varnish dried and another quarter sized spot with an oil/varnish blend that has dried. The varnish is hard and slightly amber the oil/varnish blend is more amber and wrinkled and easily scraped off with a fingernail.

[Jerry Brasch]

Thank you very much for your response, Scott. I get it now. I found a website that sells 1/2 lbs of dewaxed flake shellac and ordered some.
Just out of curiosity, do people try to put a film finish over the top of a danish oil? is that even possible? Also, is there a better choice for a wiping varnish than poly?
Again, I appreciate you taking the time to explain that to me

[Tim Howell]

Zinseer BullsEye SealCoat is dewaxed. Some people have said the spray cans are dewaxed too, but it does not say either way on their web site. I would like to know if the spray cans are dewaxed or not - anyone know for sure?

[Scott Holmes]

Tim,

If you read the fine print on the spray can; it indeed is 100% wax free.

Jerry,

Yes you can add a film forming finish over an oil/varnsih blend. Poly varnish tends to have trouble sticking well.

YES YES YES there are much better varnishes to use as wiping varnish than poly. IMHO poly is for floors. period.

Alkyd resin varnsihes are hard and clear and they don't yellow as much as poly. Phenolic resin varnishes are even harder and they are amber in color and tend to darken more with age. Poly is tough, not hard.

Poly is highly susceptible to UV damage. Phenolic resin varnishes are UV stable

[Prashun Patel]

I've used poly over bullseye shellac before. It worked for me, and it has worked for others. That being said, I have read that the wax can cause the poly not to stick. If this happens, you'll likely see the problem within minutes - not years.

Poly is a fairly light varnish vs alkyd or phenolic. A poly topcoat will make the piece appear only slightly amber - certainly not as much as the shellac.

Mixing in BLO to the mix will make it slightly more amber, and you can do that, but you'll just have to take care to wipe off excess btwn coats; you won't get a film. You will have essentially made 'Danish Oil'.

[Henry Ambrose]

If what you've done in the past works, I suggest you keep it up. If you have those supplies in your shop now -- use them.
On the other hand, since this is a mirror frame could you use only the shellac?

[Howard Acheson]

The color of varnish is determined by both the resin used and the drying oil.

The lightest varnish is one made with alkyd resin and safflower oil. Pratt & Lambert 38 is an example.
The next lightest is an alkyd resin and linseed oil. Some Cabot and some Sherwin Williams non-poly varnishes are examples.
Next, starting to get quite amber or yellow, is urethane resin and linseed oil. This is most "poly" varnishes
The most amber is varnish made with phenolic resin and either linseed oil (Behlen Rockhard) or tung oil (Waterlox Original).

[John McClanahan]

The Wood Whisperer has a podcast on this subject. Episode 128. Worth taking a look at. Then decide for yourself.

John

[Jerry Brasch]

After searching for a non-poly varnish I have come up empty handed. I guess it's not something that I can obtain locally. Sooo... I guess wipe-on poly it is. I already have it on hand and I just put my first coat of orange shellac on in a 1# cut. I'm not getting the color i was hoping for so far but i know its a little thin. I will toss some more shellac flakes in the jar if I don't see some better color after a few more coats. I'm thinking maybe I should have bought the garnet rather than orange shellac. Thanks to all who replied.

John, I watched that wood whisperer vid. I don't think i will worry about using waxy shellac under poly anymore.... At least for mirror and picture frames... stuff like that Probably wouldn't use it on a tabletop tho. Thanks much

[John TenEyck]

If you're not getting the color you want with orange shellac you can add Transtint dye to it or, better still, to Sealcoat (wax free) shellac. This is my go-to dye/toner system. The color range is infinite. FWIW, I too have used poly over orange shellac (contains wax) and never had adhesion problems - sooner or later.

John