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Marc:This is a can of Bulls Eye Amber Shellac.
It says right on the back here,
not recommended for use as a sealer
under polyurethane.
Am I the only one who when told not to do something,
pretty much does exactly the opposite?
(lively music)
I don't do this stuff
just because I have a rebellious streak.
I want to know why.
Maybe it's the scientist in me,
I just can't take someone's word for something,
I need to try it out for myself.
If you've been in the world of finishing for awhile,
you've heard that said
that you can't put wax Shellac under a polyurethane finish.
I'm sure it comes down to the wax content
providing adhesion issues for the polyurethane
but why specifically polyurethane?
There are other varnishes out there made with other resins.
Will those bind just fine?
Is it something with the urethane resin molecules
that don't bind to Shellac that has wax in it?
That's kind of the question I want to answer.
I want to use a few test boards
using dewaxed Shellac as one test.
Waxed Shellac is another
and then just pure polyurethane on the surface
as a third test.
Now, just as a little disclaimer,
this is not really a true test.
I'm only doing three boards.
I just want to see if I develop any adhesion issues at all
using the wax Shellac.
Let's talk a little bit more
about the Shellac products themselves.
The most common brand that I see in the stores
is Zinsser Bulls Eye
and it's important to know the differences
between the products that they have available.
Typically you'll see two varieties
of the regular Bulls Eye Shellac.
One would be amber and the other
will probably be labeled either blonde or clear.
Basically it just means
it's not going to bring a whole lot of color
to the wood when you apply it.
Now this is the waxed version.
It's a three pound cut, so it's relatively thick
and it's good for building coats of finish.
The dewaxed product is their Bulls Eye SealCoat.
This stuff is only sold in clear, there's no amber
or any other colors for this one.
It's just clear but it still will bring
a little bit of ambering to the wood.
Make sure you're aware of that.
This is sold in a two pound cut.
It's a little bit more dilute
which means it's more ideal for sealing applications.
At first coat, you generally want to be pretty thin
so it can soak in, dry quickly
and then you could sand it
and start applying your top coats.
These are the two products I see the most.
Now if you go to woodworking stores or shop online,
you'll find Shellac flakes.
Typically these are just dewaxed flakes
that you mix with a certain amount of denatured alcohol.
Alcohol is the thing that dissolves Shellac basically
and you can make whatever mixture you want.
You can make three pound cut, two pound cut,
down to one and half pound cut sometimes
just for spit-coats of Shellac they call them.
The primary thing that you're going to find people
using this stuff for is blotch control.
It's for stopping especially something
like cherry for instance may have pockets of grain
that absorbs more finish
so it gets a little bit spotty and dark.
Other woods like pine, certain soft woods are like that.
Cherry and maple, soft maple, there's a lot of woods
that just don't take finish very evenly.
It's important to apply a sealer first
and then apply your top coats
and that helps the stain and your clear top coats
look better on the surface.
That's why we're going to use this stuff.
Incidentally complete side note
but I want to make sure I throw out a little,
a shout out for Charles Neil stuff.
If you are looking for some blotch control,
Charles Neil recently
came out with his pre-color conditioner.
It's a water based product
and it works great for stopping blotching.
You want to check that out.
The polyurethane I'm using
is Minwax fast-drying polyurethane.
It's just clear gloss, nothing special.
It's just the cheapest stuff I could find.
Now before I apply any finish,
I need to make sure we're doing a sort of
apples to apples experiment here.
Remember I mentioned that the seal coat
is at a two pound cut.
That's a little bit more dilute than what we have
in the amber Shellac which is three pounds
so we need to make that dilution.
Diluting Shellac is actually kind of difficult
because we're talking about the dilution itself
is a volume of liquid mixed with a certain weight of solids.
Coming up with the dilution can be pretty complicated
and in fact that's why we develop the calculator
in the WoodShop Widget
and that's exactly what I use
to come up with this dilution.
Let's dilute a little bit of this stuff,
I don't need that much.
Using the calculator, I told it that I've got a quarter cup
because it's the smallest line on here.
I've got a quarter cup of a three pound cut
and if you don't see any episodes
of the Wood Whisperer for a while,
it's probably because Nicole killed me
for using her Pyrex measuring cup
which by the way is not going back in the kitchen.
This is dedicated to the shop now,
which means I'll be going to buy a new one later on.
Now a quarter cup is of course .25 in a decimal form
and the calculator said
in order to get these to a two pound cut,
I need to add .11.
That's a little bit less than half of .25, right?
Half of .25 would be next line up on here
would be basically an eighth of a cup.
I'm going to go just under an eighth of a cup.
It doesn't have to be absolutely perfect,
just get it pretty close.
Stir it up real well
and I think that would be close enough.
Since I'm going to use the same brush
for both of the Shellac mixtures
I'm going to start with the dewaxed
and then take my brush
to try to get as much of the dewaxed Shellac
out of the brush as possible
but then use that in the waxed solution.
If you go the other way,
it kind of messes up the experiment a little bit here.
This first coat is going to absorb readily.
The raw wood is going to be very thirsty
and of course using a sharpie to label this piece
probably wasn't the best idea
because it's going to run but no big deal.
Now for the waxed Shellac.
You notice an immediate difference in the color,
that amber color that it brings to it
when you use amber Shellac is really, really nice.
It's like watercolors
when you get that alcohol over the ink.
Ignore the slight blue cast to my finish.
Nothing to see here.
The third one gets nothing but the poly.
I'm not being too careful here with my brushing technique.
I'm just trying to get a nice even layer.
Now I waited a couple of hours to let the Shellac dry
and give my polyurethane coat on this piece
a little time to dry.
With my temperatures it's really all it takes
is a couple hours.
Shellac dries very quickly.
The Shellac was probably dry within a half hour,
45 minutes
but I just gave it some extra time.
Just going to remove the dust here with a
just lightly dampen paper towel.
Now each board is going to receive
another coat of polyurethane,
well the first coat for the Shellac boards
and the second coat for the poly board.
(lively music)
You might be wondering why I only put on
that one light coat of Shellac
onto each of those Shellac boards.
The reason is that's exactly how I would use Shellac.
There may be an issue here
where if you have a significant coat of Shellac
and then you try to put poly on top of that.
Maybe that's where the problems occur.
Bottom line is I don't care about that situation
because I can't think of any time
that I'm going to have a really thick layer of Shellac
and I'm just going to pile a layer
of poly right on top of it.
Anytime I use the Shellac,
it's going to be as a sealer coat,
a very light coat into the raw wood
and then I'm going to come back
with a poly on top of that as my primary top coat.
That's really what I want to know
because half of the time that's the questions
that you guys are asking me is
if I use Shellac as a sealer,
will I have a problem with polyurethane.
Hopefully that's the answer that we'll get from this.
(lively music)
With just one coat of poly,
we have a significant gloss build on here.
That's really one of the advantages
of using a Shellac under coat
is the fact that that first coat of poly
looks pretty intense.
I mean you could look at this board
which has two coats of poly
and it's pretty much the same thing.
The good thing about using the Shellac
is that it dries so quickly.
With one coat after one day, we have the same build
that it might have taken us two days to get
because we did two coats of poly on this piece.
Either way, I'm going to give it a light sanding
with 400 grit by hand
and give it one more coat on all three pieces.
I think two brushed on coats is pretty realistic
and pretty close to what I usually would do on a project.
Let's get started with some sanding here.
I'm just going with 400 grit here.
Here we go with one final coat.
(lively music)
All right that looks pretty good
so the only thing to do now is wait,
I want to give it three or four days to cure.
You can give it a little bit longer if you want to
but I think after three or four days
we should have a pretty good idea
of whether or not we're going to have any adhesion issues.
(lively music)
Now it's actually been well over a week,
I got caught up in a couple different projects
and I wasn't able to get back to this until now
but about two days ago
I decided I wanted to come up with a couple ways
to actually test the finish
and see if we could somehow pull the finish back up.
Let me show you what I did,
as you could see each board
has a number of things stuck to it.
I tried to think of what I had laying around the shop
so we've got some duct tape here,
we've got some aluminum duct tape
that you might use for putting HVAC together
and we also have epoxy
that was literally just dripped on to the surface.
Now I don't know what to expect on any of these boards.
Let alone determining a difference between them
so let's go ahead and start pulling these things off
and just see what happens.
This is our polyurethane board, just poly.
Let's start by peeling up this duct tape
and see if any finish comes off.
I don't see anything at all on the surface
so that was pretty good.
This I might need a little help with.
Now the aluminum tape, it's pretty sticky stuff,
once again no damage there.
Let's see about this epoxy,
I really don't know what to expect here,
I'm just kind of trying to ...
Hoping that I could just pop this off.
Let's try a nice sharp chisel.
That's a little bit better.
Now here's a spot where I actually
started to chisel through the wood,
what I want to look at
is the area where the epoxy just peeled up off the surface.
I'm going to see if I can't get a better result
with the bevel down.
Here we go,
that's what I'm looking for.
The epoxy definitely pulled the finish right up
and we're left with bare wood here.
Now this is the one with dewaxed Shellac
and poly on top.
Okay, no damage there with the duct tape.
This stuff is tricky to pull off.
I don't really see any damage there
so not really worried about the second one,
just try and pop those off now.
I think we're pretty much seeing the same behavior here
as we saw with the polyurethane only board
so it's pulling the finish up regardless.
All right now I would ...
It's hard to say with something like this
because this is obviously very non-scientific test
but if there were any major adhesion issues
you would expect that things like this tape,
very sticky tape would pull that finish up
at least a little bit or some evidence of it.
I don't really see anything coming up here.
Let's move on to the epoxy
and see if there's any difference in how this pop off.
All right, absolutely no difference there.
What does this prove?
Not a whole lot,
realistically this is one very poor test
to just see if we could detect the difference
in the surface that was treated with the waxy Shellac first.
I didn't detect the difference,
it behaved in the exact same way
as the other two finishes using dewaxed Shellac
as a sealer and no Shellac whatsoever.
I didn't see any evidence of a weaker bond
between the polyurethane and the Shellac layer
so I'm not prepared to necessarily say
that we've hands down proven anything here
but I think we have sort of built a little bit of a case
for the fact that that is somewhat of a myth
that maybe in some situations with some polyurethanes
or some Shellacs on some species of wood
maybe someday, somewhere,
someone will have a problem with the binding
of the polyurethane
but if I don't see any issues
and really if you think about daily abuse
and things like that, putting duct tape on the surface
and then peeling that back off,
if there was adhesion issue
I really would have to think that we would peel
a layer of finish off of there.
Of course there's a time factor here,
maybe this is something that would happen
a year or two down the line
as when you would start to see these issues occur
but I can imagine over that period of time
this finish all of the sudden just peeling off
if its bound are strongly as it seems to be right now.
The point here is to just think about these things,
I mean I just saw a recent article in fine woodworking
on finishing that specifically stated
not to use waxed Shellac
because it will cause binding problems
with polyurethane
and I'm just not seeing the evidence of it.
Maybe this video in and of itself
will bring out the folks who have a lot of experience
and years of experience who can say,
"You know what I've seen that before,"
and they could let us know about it.
I'm not refuting this
just for the sake of being argumentative.
It's just finding an answer for myself
so I can tell you safely in my shop
if I've got a can of waxed Shellac and I need a sealer
and that's what I want to use,
I'm just going to use it
even if I'm going to use polyurethane on top of it.
I don't see any reason not to at least at this point
but I always keep my mind open
because you just never know.
Hopefully you enjoyed my little non-scientific,
pseudoscientific experiment.
These kind of things are always fun for me to do
and I hope you guys enjoy them.
Thanks for watching.
(mellow music)