Why did my Shellac (Lacquer?) raise the grain? by bauerb

Why did my Shellac (Lacquer?)
raise the grain?
by bauerb

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Information:

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Bottom Line (up front)
See the Development process below...
Edited Version:

Lacquer Finishing Schedule

1. Run a damp rag over the wood between each sanding grit... Swell those little 150-grit-scratches (current grit) so's the 180-grit (next grit) takes them off easier.

2. Sand up to 220 with ROS, not forgetting step 1.

3. HVLP spray coat of clear shellac.

4. Wet sand using spray bottle of Paint Thinner (Mineral Spirits) and 400 grit wet/dry sand paper.

5. Spray coat of lacquer thinned to 13 seconds (viscosity).

6. Wet sand to 400.

7. Final coat of lacquer.

The key to a glass-like surface is:
1. Lacquer thinned properly.

2. Lay down a thoroughly wet coat of lacquer.

3. Avoid overspray by adjusting spray angle, and nozzle/flow settings.

4. Hold gun close enough to work piece.

5. Take the time to position the lateral lighting to highlight the wet-line while spraying.

6. Shellac thinner is denatured alcohol as you already know.

7. Mineral spirits and naptha do not dissolve shellac.

bauerb

After sanding some birch ply boxes with 220...

I sprayed a coat of thinned shellac.

After drying, the surfaces were very rough.

I smoothed with some 400, and that fixed it.

I was very surprised however that the shellac caused the grain to raise.

Is this normal?

Dave Arbuckle [Re: bauerb]

Yup, normal.

Alcohol picks up atmospheric moisture.

IIRC (and I may not), it will easily acquire nearly 10% water.

I don't recall at all if that's by weight or volume.

You did exactly what I do, hit it a lick with some fine grit sandpaper.

Dave

bauerb [Re: Dave Arbuckle]

I sprayed some nitro-cell lacquer over the shellac, after sanding with the 400 there is some fine powder over the shellac. I am just using a tac cloth to pick it up. Does that sound right?

BobSmalser [Re: bauerb]

Probably because you didn't raise it yourself ahead of time.

Try running a damp rag over the wood between each sanding grit...

Swell those little 150-grit-scratches so's the 180-grit takes them off easier.

Will save you a lot of sandpaper and...

A hydroscopic finish will never surprise you again.

bauerb [Re: bauerb]

ok - after sanding with 400 till nice and smooth, I sprayed a coat of lacquer.

Guess what: More fuzz. Looks like I will have to sand again, then spray more lacquer.

This is not what I expected.

I was ok with some fuzz after the shellac, but I figured after sanding and spraying the lacquer, that there would be no more fuzz. I have no problem doing multiple coats, just want to make sure I am doing this right.

bauerb [Re: BobSmalser]

Bob - I guess I learned something.

When I use a waterborne finish or dye, I always raise the grain and sand.

But the shellac and lacquer, I assumed, were Not Grain Raisers.

Guess I was mistaken.

BobSmalser [Re: bauerb]

Stockmaker's trick for finishes that are surely gonna get wet...

Raise the grain several times before applying the finish.

But I also find that doing it between grits is the absolute cat's meow to save tedium in sanding.

Joe Lyddon [Re: bauerb]

bauerb,

Would it be OK with you if I included your thread here in my Finishing collection for my website?

I would do some editing and include a link back to this thread.

Thank you!

bauerb [Re: jakesaw]

So how many sprayed coats of Lacquer should I expect to have to put down before I get a smooth surface?

I have 3 so far and still have some rough spots.

Thanks

Dan Kimball [Re: bauerb]

I'd be very surprised if it is lacquer-raised grain you feel after 3 coats. My limited experience spraying lacquer has no grain raising after the one base coat of sanding sealer. One possibility is you are spraying a too light a coat and what you feel is actually a grainy coat of dry lacquer.

jakesaw [Re: bauerb]

I haven't used much laquer - but with shellac - about 3 or 4 coats and I stop getting raising of the grain. If you use thinner mixtures of finish - it may take more coats. I but I think after 3 or 4 - you should be sanding finish not wood grain.

bauerb [Re: Dan Kimball]

Dan - you got it. The trouble was that I was spraying too light a coat, and holding the gun too far from the work.

So I was getting tremendous over-spray, combined with too light a coat of lacquer.

The overspray was settling on the work and drying with a rough feeling, that I mistakenly thought was raised grain.

I sprayed one piece today fixing my problems, and the result was 100% better.

bauerb [Re: bauerb]

So, the last coat or lacquer dried. It leveled nicely and is mirror smooth like I wanted.

Here is my new finishing schedule for the remaining three drawer(birch ply with walnut trim):

NOTE: See Up Front for the Edited, Bottom Line version.

1. Sand up to 220 with ROS.
2. Raise grain with water, sand smooth with 220 using ROS.
3. HVLP spray coat of clear shellac.
4. Wet sand using spray bottle of water and 400 grit wet/dry sand paper.
5. Spray coat of lacquer thinned to 13 seconds.
6. Wet sand to 400.
7. Final coat of lacquer.

The key to a glass-like surface is:
1. Lacquer thinned properly.
2. Lay down a thoroughly wet coat of lacquer.
3. Avoid overspray by adjusting spray angle, and nozzle/flow settings.
4. Hold gun close enough to work piece.
5. Take the time to position the lateral lighting to highlight the wet-line while spraying.

These tips may sound incredibly basic, but for a first-time sprayer, they made all the difference between a rough finish, and a mirror smooth finish.

FYI - This schedule does "NOT" produce a piece that looks like it has been encased in plastic.

It does produce a mirror smooth finish like you find in a store.

I am using this finish on my son's train table and drawers, and I think it is the perfect bullet proof finish for this.

lscraig [Re: bauerb]

Glad to hear it came out ok.

For additional finishing tips get
"Great Wood Finishes" by Jewitt.
He has a short section on spraying lacquer.

I just refinished our dining room table with deft lacquer, and it came out very nice after about five spray coats.

I used Jewett's spraying pattern method and it worked flawlessly until my kids stuck their hands in it. I finally got it all sanded out and back upstairs.

Trosey [Re: bauerb]

3. HVLP spray coat of clear shellac
4. wet sand using spray bottle of water and 400 grit wet/dry sand paper

You may want to substitute Mineral Spirits (MS) for water when wet sanding shellac. HTH

bauerb [Re: Trosey]

Trosey - I would have thought that Mineral Spirits (MS) would dissolve the shellac.
(but what do I know)

Trosey [Re: bauerb]

IIRC lacquer thinner and alcohol will dissolve the shellac but Mineral Spirits (MS) will not.

My thinking (as flawed as it may be) is that water "could" create more damage to shellac than Mineral Spirits (MS) . By all means get more input from others.

lscraig [Re: bauerb]

shellac thinner is denatured alcohol as you already know.

Mineral spirits and naptha do not dissolve shellac.

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