Finishing, finishing and more finishing

[belbein]

OK, it's been two years and change, but I finally made it back to the shop, and dived into the instruments piled there in pieces. I've started with my least favorite thing: (re-)finishing. But as always when I'm finishing, I am into something I don't understand and need some help (or maybe just reassurance).

I'm refinishing the back of the pot of my old banjo. It's a one-piece back, convex, of course. Before I started refinishing--and I don't know what the manufacturer used for finish--there was an area (circa a player's belt buckle) which looked like it had the finish worn off. So, since it looked like that, I figured it was that. But now that I've progressed through the sandpaper grits--60, 80, 120, 220, 320, 400--I find that that one part is still rough. Nothing I do makes it worse, and nothing makes it better. I'm beginning to wonder if it's not a wood grain problem, not a sanding or finishing problem.

Here are some pictures that might help.





I should note that since I'm doing a French Polish, this is step 2--pumice. So the dullness and scratches are appropriate. But this one rough part indicated by arrows--it's about the size of the palm of your hand, and everything around it is smooth and takes the finish well.

Just to be clear, the question is: are there just places in a piece of wood where the grain is such that it can't be smoothed? I can imagine that this might be particularly true with wood cut or fashioned at an angle to the grain as this convex piece must inevitably have been.

As always, many thanks for your kind advice and comment.

--Brad

PS: Oh, and I guess the OTHER question is: is there anything that can be done about it, or do I just need to accept that that part is going to be a bit different texture than the rest?

[Andy Miller]

It looks to me as if there's pore filler in the surrounding areas, but not in the area that's giving you problems. You'll need to fill that open grain with something before your topcoat starts to look nice and level.

[Marty Jacobson]

Hey Brad. Hope all is well.

It looks to me as if there's pore filler in the surrounding areas, but not in the area that's giving you problems. You'll need to fill that open grain with something before your topcoat starts to look nice and level.

+1. You need to fill those pores with something. You could spray a couple thicker coats of shellac, let them sit a week, and then level sand. That may do the trick, it doesn't look too bad. But finish is probably wicking into those open mahogany pores and with the thin mix you use for FP, it would take ages to fill. You could also make a pumice slurry with a thicker shellac cut, let it sit on there for a few days, and then level sand again.

One of the reasons I like the modern waterborne varnishes like Enduro-Var is that problems like this are virtually nonexistent. They shrink an order of magnitude less than traditional solvent-based finishes. The seal coat works as a pore filler, even on mahogany and wenge. Since last we talked, I have given up on FP except as a polishing step to gloss up finishes on old instruments or over repairs. It's simply too time consuming for new builds or complete refinishes. If you want to do FP, I'd recommend spraying 5-7 coats of shellac and letting them fully cure (a couple weeks at least) before level sanding and beginning FP.

[belbein]

Hi, Marty. Great to hear from you. Glad you're still around while I've been off doing this and that. I love the pix of the new mandos.

I'm still doing FP for a couple of reasons. One, I like the look of the only fine finish I've ever succeeded with. Two, since I'm not doing this commercially, I have the time. Three, I actually like the fact that it takes lots of relatively short sessions with waiting periods between. It kind of leavens out my normal impatience.

I want to avoid spraying if I can. What pound cut of Shellac do you think I should use?

Would clear epoxy work to fill the pores, if I only did this in this area? Remember I'm FP-ing over it.

[Marty Jacobson]

Hi, Marty. Great to hear from you. Glad you're still around while I've been off doing this and that. I love the pix of the new mandos.

I'm still doing FP for a couple of reasons. One, I like the look of the only fine finish I've ever succeeded with. Two, since I'm not doing this commercially, I have the time. Three, I actually like the fact that it takes lots of relatively short sessions with waiting periods between. It kind of leavens out my normal impatience.

I want to avoid spraying if I can. What pound cut of Shellac do you think I should use?

Would clear epoxy work to fill the pores, if I only did this in this area? Remember I'm FP-ing over it.

I'd make the shellac with high solids content and brush it on that area, then. I'd start with a 2- or 3-pound cut. The heavier the cut, the less time it will take to offgas, but it won't soak in as far to those pores, so there does need to be a balance. I think you will have problems feathering epoxy in this area, and the epoxy won't stick much with the finish and traces of lubricating oil already there. Thin CA glue could work and would be faster. But whenever you switch materials to fix a problem like this, you will see a difference in the final finish, so shellac is your best bet, in terms of finish appearance and not having the potential to make a horrifying mess.

[belbein]

Could I use a lighter cut--2 lb or less--for the first few coats to get it to sink in, then a heavier coats on top of that to get it to even out with the surrounding areas?

Also, am I right that trying to aggressively sand everything down is a losing proposition? Not that I am going to do it, but just testing my intuition.

[Ivan Kelsall]

If you use a wood filler,you might end up with an area of a different colour to it's surroundings. I'd mask off all of the back except for the area in question,& apply several thin coats of your finish to fill in the pores, & then sand the area level with the rest of the back.
There's no reason at all why you couldn't sand the whole of the back to try & level it out - but just how deep do the pores go ?. That's an unknown factor & i think that your intuition is correct & is telling you that same thing.

Strangely,the first time i saw something like this was on my front door. Just under the main Yale lock,there's an area where paint simply won't stick for exactly the same reason - it needs the pores in the wood filling = no problem with coloured paint,
Ivan

[Tavy]

Minimum 2lb cut, slap it on thick, leave for 2 weeks, then level sand (you can wet sand just fine surprisingly).

[belbein]

just how deep do the pores go

Good point. I never thought of that.

[belbein]

Little update here ... will post pix later. I took the advice of the assembled multitudes and made a slurry out of shellac and pumice. The slurry wasn't quite 1:1 by volume, but it was close (the pumice content wasn't so high that it was syrupy, but it was just on the point of thickening. Say it was about as thick as Aunt Jemima's sugar free syrup). I spread that on the open-pored section by pouring it on and trying to really work it in with a spatula, working across the grain. My theory on working across the grain was the the grain would scrape the mixture off the spatula and deposit it in the open pores. After a couple of days, I tested it by touch: it was much less rough to the touch. I then diluted whatever that first mixture was with more shellac--probably an equal volume to what I had (I know, this is not very precise)--and I laid it on once more with a soft spatula. I tested it tonight: smooth as Glenlivet 50 neat. I'm sanding now from 100 down to 220 (so far); will go to 400 or so, then start FP on Sunday. Frankly, this is like magic: how can a volcanic rock make my wood smooth? Don't make no sense. But ... it works! [Knock on wood.]

[hank]

Maybe a few drops of that Glenlivet for the final French Polishwill would be a nice finishing touch. Of course the challenge will be to keep that same bottle of Glenlivet unemptied for later mandolin finishing conversations and memories.

[Charles E.]

That looked like a dropfill application to me. Choose your fill, super glue, deft, whatever. French polish would take forever.

[Erhard Handmade Inst.]

My finish on Erhard F5-352 #3
Erhard Handmade Instruments
French Polish tech

[Marty Jacobson]

My finish on Erhard F5-352 #3
Erhard Handmade Instruments
French Polish tech

Hang on now, this is supposed to be a family friendly forum. :-)

Great job.

[Erhard Handmade Inst.]

Thank you Marty!
I dont understand this: (sorry my english is poor.)
"Hang on now, this is supposed to be a family friendly forum"

[s1m0n]

Thank you Marty!
I dont understand this: (sorry my english is poor.)
"Hang on now, this is supposed to be a family friendly forum"

The short answer is that this is meant to be funny, and has no meaning you need to decode.

"Hang on" is an english expression meaning "wait", or in this case questioning (or at least drawing attention to) something someone else has just said. "Family friendly" is an expression meaning "appropriate for children", ie, containing no taboo content. I can't see anything risqué in your post, even when looking for a humourous double entendre, so I don't what the poster was getting at.

[Marty Jacobson]

The short answer is that this is meant to be funny, and has no meaning you need to decode.

"Hang on" is an english expression meaning "wait", or in this case questioning (or at least drawing attention to) something someone else has just said. "Family friendly" is an expression meaning "appropriate for children", ie, containing no taboo content. I can't see anything risqué in your post, even when looking for a humourous double entendre, so I don't what the poster was getting at.

I was saying that the mandolin was very attractive. :-)

[hank]

I'll second that Marty. Erhard thats an amazing finish. Your French Polish technique is second to none.

[Erhard Handmade Inst.]

I was saying that the mandolin was very attractive. :-)

Thank you very much Marty!

[j. condino]

Aunt Jemima's sugar free syrup???? You've got problems way beyond finishing!

It takes me about five or six 25 minute sessions to French polish an entire instrument- far less time than I spend setting up and cleaning the spray equipment. Yours is a technique issue, not a material issue. Practice, practice, practice. Good luck.

http://www.finewoodworking.com/2007/...unburst-finish

j.
www.condino.com

[wildpikr]

Erhard,

That's an interesting headstock inlay. Beautiful finish!

[Erhard Handmade Inst.]

Thank you Mike. My logo "E" (Erhard) in the Tree silhouett Mother of pearl matherial.

[Erhard Handmade Inst.]

[Erhard Handmade Inst.]