French polishing glaze-coat question

[Tavy]

Folks I need your help,

I'm trying to improve my finishes and get closer to that impossible Holy-Grail of perfection. So far, I can rub out shellac finishes and polish to a shine - the results are really pretty good (mistakes and burn-through's not withstanding) - but I'd like to take things one step further and get that french-polished final glaze for the ultimate gloss.

The problem I have is that I'm getting little ridges in the final finish, it's not sanding marks - those are all gone - and from most angles the little tiny ridges in the finish aren't visible, but looked at under the light "just so" and they show up. They look a little like the grain lines in spruce that show up in an aged instrument, except they're on maple So basically they're marks left behind by the pad when applying the glaze. Strangely, I seem to have no problems on curved surfaces - the neck is pretty much perfect for example - likewise bowl backs seems to go OK, but it's the flat surfaces of the top and back that give me the issues.

Any suggestions for what I may be doing wrong? I'm using something around 3/4lb cut for the final glaze BTW - is that still too thick? Plus fresh used T-sheet material for the cover. Possibly I worked the back a little too much this time - how many passes do you typically make for the final glaze? One pass doesn't seem to be enough to be sure of getting an even gloss, but the more passes I make the more those little ridges build up And yes, I'm working the pad in straight lines up and down, as that's what the Milburn guitar tutorial suggests.

Many thanks in advance, John.

[Stephen Perry]

I circle. But I haven't looked for ridges! I also use a very small pad.

One thing, I keep the number of coats pretty limited.

[Mandoviol]

From everything I've read, the final coat should be pretty minimal. Also, using 000-steel wool on the instrument prior to the final coat apparently works well (though I haven't tried it yet). I'm currently becoming versed in the ways of shellac, too, and am working on figuring out how to make a good finish. A final coat of car wax over it helps protect the shine, too.

As for style of passes, etc., I've read that the pad should be in contact with the instrument as much as possible when applying shellac, and that you can apply a pretty good amount in one application if you work in a pattern; a sort of elliptical zig-zag alternating with straight strokes works well for me so far.

[Mandoviol]

I should also add that I'm doing this on a banjo-mandolin pot, not a flatback or carved top; method of application may differ there.

[Max Girouard]

On most of the instruments I have French polished, I can see the annular grain lines become pronounced after a few days of curing in both the maple backs and spruce tops. I have not seen this effect on the neck however. If I FP an instrument as the only finish, I pad on a 2lb cut until it gets built up, then I level sand with 1500 grit. I keep padding on with the 2lb cut until I can level sand with no shiny spots showing. I then use a 1 lb cut to cover the instrument. Once the whole instrument is shined up again, I start increasingly adding alcohol to my pad along with the 1 lb cut mixture. In the final stages of polishing, I'm only applying alcohol to the pad and no shellac, this gives me a glass like surface. I know everyone does it differently so you will just have to experiment to see what works for you.

[Max Girouard]

In these photos, I'm finishing up and just rubbing the pad that is loaded only with alcohol.............

[Folkmusician.com]

woo, I like that one piece back. No further input.

[bryce]

Max, under good conditions (temp and humidity) do you do multiple coats in a day or just one. Also, is there a longer wait before using just alcohol than between coats of shellac?
Thats a beautiful looking mandolin. Thanks David

[Max Girouard]

Max, under good conditions (temp and humidity) do you do multiple coats in a day or just one. Also, is there a longer wait before using just alcohol than between coats of shellac?
Thats a beautiful looking mandolin. Thanks David

Hi David,

My shop is temperature and humidity controlled so everyday is considered good conditions as long as my dehumidifier which is on it's last leg doesn't belly up before I get a chance to get a new one! I do multiple sessions in a day. I'll usually just do the back, let that dry an hour, then do the top or sides. I treat each surface of the instrument like a separate part being carful not to touch the previously padded surface which can be tricky. When it is time for another session on say the back, I'll spirit off any oil (I use walnut) then continue the session. The switching from shellac to alcohol happens in the last session, where I'll put about 4 drops of 1 lb cut of shellac and 4 drops of alcohol on the pad, rub it on, reload the pad with 3 drops shellac 5 drops alcohol, relaod then keep repeating that sequence untill I'm only using alcohol. I find that the straight alcohol padding removes most of the streaks left by the pad and I'm also using walnut oil the whole time to keep the pad nicely lubricated. There is usually enough shellac left in the pad that you are only depositing very small layers of shellac and not removing it. But I do suppose that with the straight alcohol, I am removing some of it as that is how I get all those streaks out of the surface. It is one of those things that you have to practice a lot, and get a good feel for. There may be times when I think I should stop and let the instrument "cure" for a little while, and there are other times that it feels OK to continue. For me French polishing is pretty tricky as it seems like one day I feel like I really know what I'm doing, then the next session, it could all fall apart and I'm leaving streaks big time or getting the pad stuck and leaving marks. Each time is like a new experience!

[Tavy]

Thanks for the advice Max!

I've tried again - flatter and much better this time, but still some slight streaks in the surface:



At this point I can't decide whether these will buff out (anyone use Maguiars swirl remover??), or whether to go again with the pad and risk messing it up completely again

[Tavy]

Just realized that image doesn't show the streaks, here they are pretty much at their worst:

[amowry]

I never had much luck going in straight lines like the Milburns suggest. For me, going in circles leaves fewer ridges. It may just be my technique. Actually, I've gotten to like the slight texture that is left-- it gives it more or an organic look and feel. To me your finish looks great.

[Max Girouard]

Yeah that does look great. I also go in circles. For final polishing, I use Meguiars PlastX first followed by #9, then #7.

[Tavy]

Thanks Max and Andrew - unfortunately this story does not have a happy ending - I buffed it out and got it looking pretty good, then figured I'd do some work elsewhere on the instrument and completely destroyed the finish on the back. I don't think the marks are that deep, but the thing looks like it's been in a war zone - evidently I hadn't left the finish long enough to harden after the glaze coat before handling and it scuffed up all over while I wasn't watching

I tell you I really wanted to smash the whole thing against the nearest wall when I spotted that!!

So I'll have to give it a few more days (not only to calm down some!), then see if there's enough finish left to sand level again and reglaze....

Still I guess that gives me some time to order more Maguiars!

[Max Girouard]

Man that stinks!

I had a mando that I had recently french polished, came out perfect. I let it cure for a couple of weeks, then strung it up. It was in March when we had all that strange weather, 80 degrees and humid. Anyway, I set it up and started playing it. About an hour later, the room had warmed up considerably due to the sky light, and me being in it (very small room) and when I went to put the mandolin away, I had to peel my shirt off the back. That left a nice little cotton weave pattern on the back! I've had other mandolins that had only cured for a week that were fine, so to be safe now I plan on letting it cure for at least a month before letting it touch anything.

[amowry]

I've been there, and that's the main reason I switched to an oil varnish recently. However, I still think French polishing can yield a great finish, and I wouldn't despair. The best we can do is chalk these things up as learning experiences ):

[HoGo]

Was your shellac new, Max? What kind of shellac do you use?
I did experiment how fast I can finish mandolin, so I airbrushed concentrated dye withe shellac added for color layers (wood bindings, so I ddidn't want stain the wood directly) and from there straight french polish. Two days, some four sessions were enough and the next day I strung the mandolin up. I was afraid the bridge may stick but it didn't, barely left a mark.
I typically do the back then back of headstock, this is enough cure time to turn the mandolin around and do the top.

[Max Girouard]

Was your shellac new, Max? What kind of shellac do you use?
I did experiment how fast I can finish mandolin, so I airbrushed concentrated dye withe shellac added for color layers (wood bindings, so I ddidn't want stain the wood directly) and from there straight french polish. Two days, some four sessions were enough and the next day I strung the mandolin up. I was afraid the bridge may stick but it didn't, barely left a mark.
I typically do the back then back of headstock, this is enough cure time to turn the mandolin around and do the top.

Yep, my stuff was less than a couple of weeks old. That is how long it took to dissolve from flake, and then I pretty much used it after filtering it. I've made several batches from the same lot with no problems, except for this incident. I asked a customer about the mandolin that went out before it and he had no problems!

[HoGo]

Maybe I'm lucky guy, but my shellac dissolves overnight and dries perfectly. I hope the art shop I buy from won't change suplier :-)
I bought some bleached shellac but never got to using it and that may be too old now to use.
Back to OP. You say you use circi]ualr motions and the "streaks" you're referring to seem to go vertically so I'd guess it's just grain showing, Pretty typical. FP is too thin to cover texture of wood completely. After some drying it will telegraph everything that's under.

[Mandoviol]

We keep our shellac measured out into 1 oz. amounts inside old medicine bottles. Keeps it dry and airtight. It dissolved pretty quickly overnight, and it's a year old.

I haven't had the problem (yet) that you did with that one mandolin, Max; I'm hoping I don't run into the same problem (living in Virginia during the summer--hoy). As far as I know, Maguiar's car wax over it helps protect it pretty well; might be that a wax-layer would keep heat from affecting the shellac.

Tavy, if you gummed up the finish, what about rubbing it with some alcohol and rubbing the ridges out? That should melt the shellac back down and make it possible to fix the finish. (Though I don't know if it will have other effects--if this is a stupid idea, please, somebody, correct me!)

[Bill Snyder]

I know that you already have the application part down but take a look at Frank Ford's article on French polishing. The part that you probably want to take note of is on page 3 where he finishes off with his bare hand. Maybe this would be of help to you.

[Tavy]

Thanks for all the kind words everyone - good to know that others have been here before - to be honest messing this one up was my own fault - I knew I was pushing the envelope a touch on the drying time

Max - your experience sounds familiar too - this being the UK, it's always cool and humid here, and since I don't have the luxury of climate control, getting the stuff to harden can be tricky at times. I've also found that different fabrics have differing tendencies to stick and/or imprint on the shellac. I've not had any issues with cases, or the hard base of bridges strangely, but "furry" fabrics like carpets and wooly jumpers can be killers if you're not careful early on.

HoGo - I'm impressed you can finish so fast, I certainly couldn't. I have done touch ups at least as fast as that though - but only working outdoors on a sunny low humidity day so the stuff is basically "instant dry". Unfortunately those are rare round here at present!

[Tavy]

Time for an update, first here's a pic I took of the damage I'd put in the finish:



Fortunately I was able to sand very nearly all of the marks out with 1500 grit, I had thought the finish had gone too thin in places to take a shine, but no, wiping over with nearly neat alcohol put the shine on nicely. I then finished as per Max's suggestion - Meguiars PlastX followed by #9 then #2.

Wish I could look this pretty when I'm 100+ years old



And one of the reflections - most of the marks/swirls you can see here are actually reflections caused by the back being anything but flat :



One comment though - the PlastX is quite abrasive - you can actually hear it cutting as you polish. I tried it first on an "old" shellac surface and it didn't do too much, but on a "fresh" surface (about 4 days since I'd put on the final glaze) it definitely left scratch marks. Those pretty much polished out with the swirl remover, but it was scary for a moment there It's definitely a useful tool in the armory though.... seems to be less aggressive than 2500 grit, while still being able to "cut" .

Time to leave it for a while now before I try and string up....

[Max Girouard]

Another thing to note about the PlasX is that you have to get all of it off after polishing. I left a spot on the back of a peghead once and it ate the FP. Looks great!

[Jim Hilburn]

I had Novus #2 recommended to me and it does work very well.