Grain Filler weaken adhesion?

[Nick Sorenson]

I noticed that my conventional lacquer is pretty brittle over open grained woods (particularly Ash). It's pretty flaky with any abuse (even the lightest hit or a screw going through it), it just chips right off. I haven't noticed this with woods I'm not filling. So, I think it's got to be something with my pore filler.

My schedule:

-Sand to 180 grit
-Pore fill against the grain
-Clean with paper towel cross grain
-dry for 5 hours
-Spray a wet coat of lacquer (x3 or 4 coats)
-Sand to 220

and at this point it's already pretty easy to chip off if I try. Much more so than with woods I haven't filled.

[Scott Holmes]

Without specific product names etc. we can only guess.

My 1st guess is the grain filler has not completely dried and ready for a top coat in 5 hours.

Many fillers are not compatible with certain finishes and vice-versa. Are you using the sealer/filler spec'd for your lacquer?

[Bob Wingard]

For once .. I'll have to totally agree with Scott ... brand names would be most helpful, but going on the limited information given, I would have to assume you have adhesion problems from not sanding the fill back expose bare wood. You are essentially trying to topcoat the pore filler, which is a lot like trying to topcoat dirt & dust.

You stated that you "cleaned" with paper towels .. let dry .. sprayed lacquer. I'd bet your cleaning left behind enough debris to cause your adhesion problem. Even at this point, you should be able to sand to bare wood and shoot it again, but I don't think that's exactly what you wanted to hear.

[Scott Holmes]

Bob picked up on something I missed...

-Sand to 180 grit
-Pore fill against the grain
-Clean with paper towel cross grain
-dry for 5 hours

You are supposed to sand filler back, not wipe it clean... you want to sand with the grain to flatten the surface (assuming it's a flat surface and not a curved surface). Leaving the filler in the pores; nothing on the surface. then you will need to wipe it clean to get all dust off the surface.

[Nick Sorenson]

thanks! It's funny how both of your signatures are conflicting and yet both true. LOL... I do think anyone can learn to finish. And it's definitely an art and a science.

[Tony Bilello]

I have never heard of this happening before.
What are you using for a grain filler?
Is that grain filler compatable with lacquer?
Have you read the directions on the can of grain filler?

The problem more than likely is either you are using incompatable products or you are doing it wrong. Where did you come up with using paper towels for cleaning? You should be using a burlap cloth which is somewhat absorbing but very abrasive and coarse enough to not pull the filler back out of the pores.
I have seen people spray surfaces that were not completely cleaned like they should be and still not have that problem. Your surface must have been extremely poorly prepared for that to happen or again......incompatable products.
The others have already asked with no answer so I will ask again, what did you use for a filler? This is more than likely where the problem lies.




]

[Bob Wingard]

What are you using for a grain filler?
Is that grain filler compatable with lacquer?]

Just out of curiousity ... what would you consider "incompatible" combinations of FILLER vs. TOPCOAT ???

[Tony Bilello]

Just out of curiousity ... what would you consider "incompatible" combinations of FILLER vs. TOPCOAT ???

Hmmmmmmm. I posted earlier but it didn't go through. My internet service sucks lately.
To be honest Bob, I don't know what I would consider compatable. I buy all my finishing products and they are predictable. The original poster never answered the requests for what grain filler he used so there is no telling what he used which might even be some home made concoction.
I also agree with you and Scott about sanding back. I normally apply grain filler over a wash coat of primer. do the burlap thing and then sand the whole thing back to bare wood leaving the filler in just the pores and deeper grain lines.

[Bob Wingard]

Your post simply got me to thinking ... with all the talk about incompatibilities in finishes, I couldn't think of any REAL conflicts between any filler/topcoat combinations, assuming proper application. I'm sure, someplace out there, somebody has found a pore filler that's based in something not compatible with something else, but I can't think of any off hand.

I use tinted drywall compound .. cheap, easy to tint, easy to apply, dries fast, sands ultra smooth. Naysayers claim it shrinks too much ... how much can the quantity stuffed into a PORE shrink ??? Even if it did ... it's just trapped there beneath the topcoat ... it's not going to rattle loose or anything like that. Now ... what might I put over the top of that, that could cause problems ??? Nothing I can think of. If one were to apply a water based finish over it and REALLY rub it around, I guess you might be able to pull some of it out of the pores, but you would have to really work at it.

Assuming the use of solvent based pore fillers ... again, what can you put over any of them that would cause any problems ???

Are there any pore fillers that are based in a medium that is known to have issues with any topcoat out there ???

Just wondering !!!

[Tony Bilello]

......I couldn't think of any REAL conflicts between any filler/topcoat combinations, assuming proper application. ....
It might be possible that the OP made his own slurry of varnish or polyurethane and then applied lacquer over it. Tony B

I use tinted drywall compound ..
At one time, plaster was very commonly used as pore filler. Tony B

Just wondering !!!

There is no tellin' what he used.

[John Coloccia]

Silicone caulking for filler would cause problems for sure...

...
...

:D

[Pete McMahon]

Bob,what are you using to tint your drywall compound?
As far as filler shrinking; it's not going to rattle out so to speak but can create a "hungry" look to a formal finish that's supposed to be flat.

[Bob Wingard]

I've used everything from COFFEE/TEA/FOOD COLORING/TRANSTINT/whatever water based dye or colorant that will get me the color I need.

[Pete McMahon]

Ever have those colorants fade or bleach dramatically?

[John Coloccia]

FWIW, I know more than one luthier that has used drywall compound with great success. I think they tend to tint darker than the surrounding wood.

Most of the compatibility issues I know of, or really finishing process/system issues, usually apply to metal and fiberglass finishes...things like that. It has to do with things like etching aluminum, properly priming and top coating to prevent corrosion, proper sanding and removal of contaminants, etc. For example, if you wanted to paint over powder coat, just spraying paint over it will not be optimal. You need to scuff, primer would be nice, etc. Not so much incompatibility as using the correct process.

Wood finishes tend to be pretty forgiving with a little common sense. For example, I probably wouldn't apply BLO over polyurethane though maybe Danish Oil over poly might work (though I can't imagine why I'd do that).

It seems like there's a way to put practically anything over anything else with the right cocktail of chemicals and the correct process.

[Bob Wingard]

Ever have those colorants fade or bleach dramatically?

Not that I can tell ... sometimes I'll tint the filler ighter or darker than the rest of the project for effect, but I can't say I've ever noticed fading. I would guess that even if it did occur, it wouldn't be very noticeable.