Shellac between transtint and poly?

[Chris Atzinger]

I am spraying a cabinet project this weekend (I hope). The project is a combination of maple ply, solid wood, and quilted veneer. I am using transtint dye to color, and the topcoat will be General Finishes Enduro Poly satin finish. Do I need to spray a seal coat of shellac between to the dye and the poly?

Thanks!
Chris

[Scott Holmes]

It's not an absolute requirement but sealing the dye in place with shellac is a good practice. The drawback to TransTint dyes is the the alcohol in the shellac can cause the the dye to bleed, drip or move about. The waterborne General Finish could also do the same since the the TransTint is also water soluble. Sealing a water only dye (TransFast) would be a big benefit from the shellac seal coat. The shellac will seal it in without re-dessolving the dye.

Spray carefully either the shellac or the waterborne finish and you will be fine. The other advantage to the shellac is that it will warm up the dye color before the waterborne as many of the waterborne finishes give the wood a blah look.

[Rich Engelhardt]

Do I need to spray a seal coat of shellac between to the dye and the poly?
Shellac under poly of any brand is a recipe for disastor...

[John Coloccia]

Poly is certainly fine over dewaxed shellac. As far as I know, it's fine over non-dewaxed shellac too. I have never heard a first hand account of a finish disaster because of this, though I'm sure it must have happened to someone at some point.

[Rich Engelhardt]

Poly over regular shellac has well over 40 years of history.
The labels on poly are pretty specific about not using it over shellac.


Dewaxed shellac was never specified.

[John Coloccia]

Rich, I know flooring installers that use dewaxed shellac (nearly always Sealcoat) under poly. Over the years, I have not ever heard one instance of failure over dewaxed shellac. Honestly, I've not even heard of one instance of poly failing over non-dewaxed shellac either. I know about the admonishments on the can. I also know that Zinsser specifically recommends SealCoat under nearly all finishes, including specifically waterbased polys. I think at most you shouldn't coat over waxy shellac (which is a good idea anyway), but I'm even suspicious of that at this point because people do it successfully, and I don't know of anyone that's done it unsuccessfully.

I think this is just a myth that poly manufacturers just perpetuate because better safe than sorry.

[John TenEyck]

I agree with others who have said poly is fine over at least dewaxed shellac. I have used GF's WB Hi Perf. poly many times (gallons) over Sealcoat shellac, for several years now, with no problems. It passes any scratch or tape test I have tried.

To the OP, as long as you spray the topcoat it will be fine. Scott's advise to spray the first coat lightly is good. You want to avoid any runs with the first coat. Obviously, test everything on scrap first. Shellac, even Sealcoat, will change the look, which may or may not be desirable. I'd only use it if it has a desirable impact on the look you're after, or if your WB topcoat results in undesirable raising of the grain. In that later case, the Sealcoat really makes life easier.

John

[Rich Engelhardt]

John,
There's two reasons why the (poly) manufacturers don't recommend putting their product over shellac.

#1 - The manufacturer has complete accountability for the performance of their top coat when only their products are used as both sealer and finish. They do their product performance testing using their products and not a third party material. There's nothing wrong with this & it's not a way to just simply sell more product - although that aspect is a byproduct of it. Polys are pretty finicky when it comes to adhesion. As has been mentioned numerous times here in the past, they do often have problems "sticking to themselves".
You can't fault a manufacturer for wanting some sort of control over how their product is applied if/when they are "on the hook" so to speak for it's performance & it has known adhesion issues.
(for the sake of brevity - I'll stop there)

#2 - Since it's introduction some 40 plus years ago, polys have always had issues going over shellac. That aspect of the product is well known and well documented. That's why the manufacturer is specific when they warn about applying it over shellac - or sealers with sterarates too.
Both have caused adhesion issues in testing.

I have had several complaints come before me in the past where shellac did cause issues with poly.
Since I sold the stuff for a couple of decades and came in contact with who knows how many thousand users, I admit I had a much greater chance of seeing those issues than most other people.

As far as people not having any issues even after years of using poly over shellac...
Thousands of people have one too many every day, then hop in the car and weave their way home. Only a very tiny percentage of them get in an accident or get picked up.
( I know that's an over the top way to put it - but --sorry it's the best analogy I could think of)


Re: dewaxed shellac.
Dewaxed shellac was never specified or mentioned.
It's not the same product.

I don't know if not specifying dewaxed shellac was an over sight or not - I like to believe it was.
Dewaxed shellac or Zinsser Seal Coat would be the correct material to use.

[John Coloccia]

Here is a water based poly (notoriously less "sticky" than oil based) that I just happened to know the name of, and you can read what it says under "Previously Finished Floors".

http://www.duraseal.com/products/finishes/water-based-polyurethane/



PREVIOUSLY FINISHED FLOORS


Note: Do not apply over wax, lacquer, stains or shellac containing wax or stearates. Be certain floor is free from all wax or oily residue.




Maybe the lesson here is to buy from a manufacturer that understands their product, or updates the instructions. As far as I know, Sealcoat was the first commercially available, premixed dewaxed shellac. I can only assume that when people said "shellac" that it referred to commonly available waxy shellac. Zinsser (Rustoleum, I guess) guarantees Sealcoat compatibility under all clear finishes. There must be a clear finish out there it's not true for. For example, it can cause EM6000 to craze because of some occasionally chemical incompatibility. That's the only one I know off the top of my head, though.

[Bob Wingard]

I believe product performance liability is a major element in the warnings on poly cans ... they don't know if you're going to put their product over some elcheapo 10 year old crap, or some ultra refined fresh stuff made up with pure grain alcohol ... so ... they just tell you not to do it. If you have a complaint .. call them .. they find out you didn't follow their warnings to the letter .. your problem, not theirs.

Their poly may stick just fine to one brand of shellac, but not to another ... they're simply NOT going to go out and test every brand they can find for compatibility ... they simply say don't do it, and their liability pretty much ends right there if you did use it.

[Chris Atzinger]

Hi Guys,

Just to clarify, I was planning to use 2lb cut of ultra pale dewaxed shellac that is fresh (as in, just made this morning fresh). I ordered both the shellac and the GF enduro poly from Homestead Finishing, and asked Jeff whether or not it would make things easier to spray the shellac as a sealcoat. He thought it woul give the quilted maple veneer some depth, but not necessary otherwise.

Is there any other benefit to using it? Will it do anything to make the poly go on smoother/easier? I am new to spraying and new to this type (waterborne poly) finish.

Thanks!
Chris

[Rich Engelhardt]

John, (or anyone else for that matter)
Please go back and reread the first two posts of this thread.
Tell me where dewaxed shellac was mentioned.

[Scott Holmes]

Rich you are correct, both of us failed to mention dewaxed in our replies. Should have said Zinsser Seal coat or dewaxed shellac as a seal coat.

[Rich Engelhardt]

Scott,
I figured it was an oversight on your part.
I've seen/read too many of your posts before where you caution about using anything other than dewaxed shellac.

[Chris Atzinger]

Hi Rich,

Same here. I should have been more clear. I only use dewaxed shellac that I make-up myself. Thanks for everyone's input. It's been very helpful!

-Chris

[Rich Engelhardt]

Chris,
The devil is always in the details.
I worked in the paint industry from 1966 to 1987 selling all different type of paints and coatings.
We'd often get professional painters come in the store alongside the retail customers. If we were busy putting together an order, the two (retail and pro) would often mix.
The pro's would offer up their pet way of doing things to help the retail customers. It often ended up a train wreck....

999 out of 1000 times it was because some critical detail was overlooked or assumed or a simple misuse of terminology.

Back in the 60's and 70's, all the painters called B*I*N simply Bullseye. (you can see where this is headed...)
One day, Joe the painter comes in. We're busy. He tells me (or someone else) to grab him two gallons of Bullseye on our way up front from the back room.
Then while we're busy, he tells Mrs. Jones she needs to seal her pine wood work with thinned down coat of Bullseye shellac (one quart of shellac to two gallons of alcohol) before she stains it.

Joe gets his B*I*N & heads back out to the job..

Mrs. Jones picks up a quart of B*I*N - after all - Joe asked for Bullseye and we gave him B*I*N right? Must be the same stuff. - and two gallons of alcohol.
She heads home, mixes up the B*I*N and alcohol - and proceeds to seal as much woodwork as she can.
Despite the fact that it was all going on white, she continued to do it - thinking it would somehow be all right once the stain was applied.Naturally - it wasn't..

Back then, customer complaints were handled different. You didn't just refund the price of the materials. You did what you had to do to "make it right" - as long as the customer didn't mention anything about legal action....as soon as that happened, our hands were tied & the whole thing turned over to the legal department. 90% of the time, it would end up in our laps anyhow when the legal department talked the customer into letting us try to rectify the problem before it went that far.

Back then,,,I was also "low man on the totem pole", for all five of the company stores in the Cleveland market. I got to do all the grunt work when stuff like his came up.
"Making it right" for Mrs. Jones, involved me taking a case of alcohol, a ream of fine grit flint sandpaper, a couple of rolls of EZ Mask - and about a week of my time - sanding and flushing the wood work - then staining it.
The actual work wasn't bad - but - Mrs. Jones wasn't at all happy about the whole thing & I heard about it constantly.

I sort of think of these online forums in the same way as working in the paint store way back when.

Scott is a (deservedly) well respected professional in the finishing field. I'm sure he's put a lot of time and effort into getting there. People take his advice verbatim.
This part of SMC is also open to search engines.
I can easily picture someone doing a google search for General Finishes Enduro AND shellac, stumbling across the advice to use - shellac as a sealer - especially if the advice comes from a well respected pro.
Maybe it would work out fine for them. Shellac is unpredictable like that. Maybe they would be one of the unlucky ones that run had on into a compatibility problem.

[Jack Clark]

What about the old adage: "Shellac sticks to everything and everything sticks to shellac" ?

Maybe it should be revised to: "Dewaxed shellac sticks to everything and everything sticks to dewaxed shellac..."

[John TenEyck]

Rich, your horror story is a perfect example of why you should always make test samples before committing to use a product or process on your project. It's the user's personal responsibility to do so. With the regards to your story, I can't believe your company spent time and resources to fix that lady's problem. If your store did not recommend using those products together, why would you feel responsible to fix it? A high level of customer service is one thing, but fear of litigation shouldn't be what's driving it. I wonder if there's more to the story that you left out.

John

[Rich Engelhardt]

I wonder if there's more to the story that you left out.
The company's headquarters was in Cleveland.
Everybody was a friend of somebody or another.

When a ""suggestion that we make the problem go away", came down from way above we did what we had to - within reason.
In the above case, it was either replace all the wood work, hire it out to a painting contractor- -
or send out the "kid" (@ $1.50 an hour) w/six gallons of alcohol (~$6.00 @ the time), some cheap flint sandpaper and two rolls of EZ mask (that were over age & had lost most of the adhesive & had been written down to no value).

Also - keep in mind that this was also some 40 years ago.
The concept of customer service was a lot different then.
(heck, the guy that pumped your gas @ the service station wore a tie, cleaned the windshield, checked the oil & radiator and filled the tires w/air - all for $.29 a gallon)
Customer complaints were viewed as an opportunity to increase sales via building better customer relations.

There really wasn't any fear of litigation back then either.
Having someone say, "I'm going to sue" was, 99% of the time, just an empty threat/ fairly common expression.
99% of the people that said that had no intention of taking it to court.
It was exactly like someone saying, " I'm going to kill you for doing that".
However - there was always a chance it would be that 1% - so - as soon as the customer mentioned any sort of legal action, the conversation was over.

BTW, this all pertained to retail customers.
The commercial and professional trade was handled different.
I still did more than my share of grunt work for them though....