Shellac under poly for floor finish?

[Michael Weber]

Got my stairs mostly sanded. Thanks to all who suggested improvements on how I had planned to do that. Turns out a couple coats of amber shellac matches the flooring color on the first floor pretty well. Any reason not to use shellac with poly over it for a finish on the treads? Or should I keep mixing different stains trying to get a near match? Thanks. Oh yeah, would I need to use a wood conditioner if I use the shellac? Wouldn't think so but the conditioner makes a big difference using stain on my samples.

[Mike Henderson]

Use the dewaxed to make sure you don't have any adhesion problems. Should work fine.

A lot of people use dewaxed shellac as a sanding sealer.

Mike

[george wilson]

Nothing sticks to shellac except more shellac,or maybe another alcohol soluable finish. Put on to much,and you may find your poly coming loose like layers of saran wrap. I'd at least sand the shellac to get a mechanical bond.

Why don't you get some honey amber liquid Trans Tint dye from Woodcraft,and see if it blends into a sample of he poly. That would be a better way,and would give the right color.

Let me warn you: poly may not stick to itself very well,either. Follow the directions as to recoating times,etc.. I've had it come loose in layers on a floor I had a contractor paint in my last house.

[Frank Drew]

Michael,

Are you sure the poly by itself wouldn't give you the color you're after?

Anyway, I don't think you'd have trouble using shellac under another finish if you scuff up the well-dried shellac with sandpaper to provide a mechanical bond with the top coat. Shellac isn't a stain or dye, and it's certainly not water based, so you don't need a conditioner underneath it.

Dyes tend to be somewhat more transparent than stains (i.e. clearer coloring under finish), if you go that route. Some dyes aren't light fast, though, so if the stairs get direct sunlight check with the dye's supplier before using to see if it will be appropriate.

[Howard Acheson]

>> Nothing sticks to shellac except more shellac,or maybe another alcohol soluable finish.

That is not true. Shellac is a sort of universal sealer frequently used as a barrier between incompatable finishes. Actually, shellac sticks to anything and anything will stick to dewaxed shellac. However, oil based poly and waterborne finishes should not be applied over a shellac containing its natural wax. They will not adhere well.

[Howard Acheson]

>> Any reason not to use shellac with poly over it for a finish on the treads?

No, shellac makes a fine undercoat. But you must be sure to use a dewaxed shellac. Zinsser Amber is not dewaxed. Oil based poly and waterborne finishes will not adhere well to shellac that contains its natural wax. The only pre-mixed dewaxed shellac is Zinsser Seal Coat. (http://www.zinsser.com/product_detail.asp?ProductID=72)

[Mike Henderson]

There's a real color difference if you use water based poly. You just don't get the rich reddish-brown tint that you'd expect with the oil based finishes. Using dewaxed shellac under water based poly is a good way to recover that tint.

I have great respect for George, but I disagree with him on using shellac as a undercoat. If you use dewaxed shellac any other finish will adhere to it fine. In finishing classes I've taken, they recommend dewaxed shellac both as a sanding sealer underneath any finish, and as a way of making sure you get adhesion between coats of incompatible finishes. For example, you have a piece of furniture which you want to refinish and you're not sure your new finish will adhere well, they recommend shooting a coat of dewaxed shellac first. The dewaxed shellac will adhere to the old finish and the new finish will adhere to the dewaxed shellac.

Also, if you look on the can of dewaxed shellac, it will say that it's a universal sealer. The manufacture date is always on the bottom of the can so make sure you get a fresh can. Sometimes the cans sit on the shelf for a long time and the finish can go bad. Don't use it if over three years, and you'd prefer fresher.

George is correct on coats of poly. Poly does not bleed in (unless you do the coats fairly close in time) so you need to scuff up the finish to get adhesion for the next coat.

Mike

[Michael Weber]

Another question. I've read online how to dewax shellac. I have a can of amber waxed shellac that has been undisturbed for several weeks. I notice if I insert a screw driver down to the bottom it comes up with a darker residue on the very tip. Can I assume the top half or two thirds is safely de-waxed and if I pour carefully through a filter it will be usable as such? I can go through the whole recommended de-waxing procedure but time is a constraint and if I can at least start with a first coat today it would be a big help. Thanks for all the advice.

[Mike Henderson]

Another question. I've read online how to dewax shellac. I have a can of amber waxed shellac that has been undisturbed for several weeks. I notice if I insert a screw driver down to the bottom it comes up with a darker residue on the very tip. Can I assume the top half or two thirds is safely de-waxed and if I pour carefully through a filter it will be usable as such? I can go through the whole recommended de-waxing procedure but time is a constraint and if I can at least start with a first coat today it would be a big help. Thanks for all the advice.
I wouldn't take the risk. You can do it yourself but why risk it? The dewaxed shellac is cheap and the company has good processes to remove all the wax.

Mike

[george wilson]

I'm not going to argue the shellac topic again. Do be careful about the poly not adhering to itself,though.

[Michael Weber]

I wouldn't take the risk. You can do it yourself but why risk it? The dewaxed shellac is cheap and the company has good processes to remove all the wax.

Mike

Mike, George and all. Your advice and recommendation are appreciated. Not sure what's going to happen with the finish but at least I'm much better informed now.

[Cody Colston]

Like Howard said, Shellac is used universally as a barrier between incompatible finishes because most any finish is compatible with and will adhere to Shellac.

Polyurethane does not "burn in" like lacquer or shellac so sanding is necessary between coats for good adhesion. Sand too hard on cured polyurethane and you will begin to see the various layered coats emerge.

BTW, anyone want to start a pool on how long this thread lasts before it gets moved to the "Finishing Forum?" :D

[Michael Weber]

Like Howard said, Shellac is used universally as a barrier between incompatible finishes because most any finish is compatible with and will adhere to Shellac.

Polyurethane does not "burn in" like lacquer or shellac so sanding is necessary between coats for good adhesion. Sand too hard on cured polyurethane and you will begin to see the various layered coats emerge.

BTW, anyone want to start a pool on how long this thread lasts before it gets moved to the "Finishing Forum?" :D

Cody, I thought about putting it in the finishing forum but I needed a quick answer and this is the most active forum. Anyway, I poured off over half the can of amber shellac before another thread of color started to appear. Kind of lighter but milky looking. Guessing that was the wax. We'll see what happens. Going to be :D or maybe :eek: