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View Full Version : Cure for a dent in an uke top



Chris_H
09-26-2013, 06:16 PM
I just put a dent in a spruce top of an uke I have been waiting months to finish. It is about 1/8" long, and shallow, but way too deep to rub out. I am ok with it, this is going to be a player for me. It makes me sad to see the dent, as all else is good. The lacquer finish is pushed in, but intact, not cracked.


I just finished carving the neck, ready to finish it. This one is finally ready to put together.


How can this be fixed..?

Cheers!

new wave ukulele
09-26-2013, 06:26 PM
A wet paper towel and a soldering iron to steam the ding out

tomas13
09-26-2013, 07:19 PM
Same thought as what Eric has suggested.
Here are two tricks for repairing both dings and holes
in soft-wood tops from Mr. Frank Ford's wonderful site at frets.com:

http://frets.com/FretsPages/Luthier/Technique/Finish/SteamOut/steamout1.html
http://frets.com/FretsPages/Luthier/Technique/Structural/SpruceHole/sprucehole.html

Tomas

(ps - sorry, several photos seem to be missing in the first link)

Moore Bettah Ukuleles
09-26-2013, 08:50 PM
That works on raw wood but are you sure it works when there's a finish on it?

Beau Hannam Ukuleles
09-26-2013, 09:41 PM
That works on raw wood but are you sure it works when there's a finish on it?

Exactly. Don't do this with finish already on

Beau Hannam Ukuleles
09-27-2013, 04:48 AM
I just read the link to frank ford. Seems you can do it!! Another day, another thing learned,, so it was a good day :)

Timbuck
09-27-2013, 05:07 AM
I've done it with shellac finish..I made a little dam around the ding with Bluetack, filled it with water then carefuly dipped in the the tip of the soldering iron to make the water boil...It removed the ding ok but It also brought out lots of tiny bubbles in the shellac :(...so it needed to be refinished afterwards.:o
I won't use that method next time.

Chris_H
09-27-2013, 05:38 AM
That definitely works with raw wood, different species responding better than others, sometimes the dent completely disappears. I use that technique often.

Under lacquer..
that scares me A LOT. It seems really dangerous, though maybe it works? I am happy with the finish overall, and do not want to refinish it. I was careful to keep this finish thickness to a minimum. It does not have the deep plastic gloss finish, more like a nice French polish. I cut the top flat about 4 months ago, the grain is now very faintly visible in the sheen, very happy with the finish. Refinishing the top, would kind of be a disaster, I would never get the lacquer to this thickness again, If the finish was damaged, and blond wood exposed, some 'staining/ bleaching/ discoloration' could, probably would happen.

I read the links, in the case of steam swelling the dent, he was also buffing after, which makes sense. There is sufficient lacquer thickness on this top for one final very light buff right before the bridge and neck go on, and not much deeper. I almost want to try it just to learn, but will try it on a scrap sample first another day. I don't want to put water and heat on this top. It may be a 'build it, and ride it hard' sort of deal..

Timbuck
09-27-2013, 05:54 AM
I remember having a bit of a success a couple of years ago by repeatedly wetting a dent from the inside of the uke, with warm water applied on the tip of my finger I also used a bit of washing up liquid as a wetting agent... the next day it was almost gone.

PhilUSAFRet
09-27-2013, 07:48 AM
PS: Just a quickie, if you go for the soldering iron trick, use a spatula tip if you can.

Michael N.
09-27-2013, 08:28 AM
There's not many finishes that can withstand the heat of steam. The chances are that it will mar the finish - to some extent. You are left with the option of repairing the finish or not steaming the ding out but 'filling in'. If it was a Shellac finish it's not that difficult, but that depends on how deep the depression is. On small shallow dings it's sometimes filled in with Shellac and gypsum.

Chris_H
09-27-2013, 02:48 PM
yeah, I think this ding just gets chalked up to 'be more careful'. It was a stupid mistake. Careless. My initial gut reaction (based on my experience) was that it was just too bad, so sad, not gonna be fixed. I have wondered about a patient filling with lacquer (months) then careful scrape and buff. I was kinda hoping to hear some magic. I am not going to mess with heat and water. That says 'repair finish after' all over it. I am super happy with the finish overall, the dent will have to stay.


Thanks for all the replies.

On a shellac finish, what purpose does the gypsum serve? is it filler? Does the gypsum stay clear when in suspension with the shellac? I know gypsum is crystalline by nature, even optical in it's purest forms. If so, I wonder about gypsum in lacquer? That would help minimize shrinkage. I mix my own fillers (for under lacquer) by using lacquer as a binder with the exact wood dust, or, by using varnish as a binder, mixed with the exact wood dust, for under oil finish.

Michael N.
09-28-2013, 03:18 AM
Yes, the Gypsum acts as a filler. A bit like pore filling with Pumice. The Shellac 'clears' the Gypsum. I've tried it a few times on shallow dings. It's not absolute perfect. You might see a very slight cloudy appearance but it's a pretty good method, far quicker than trying to fill with Shellac alone. You 'french polish' the stuff on - bit of Gypsum, bit of shellac added to the outside of the pad. You can also use Pumice but that tends to abrade the surrounding finish a lot.

UkeKiddinMe
09-28-2013, 03:29 AM
And then when you're all done with these repairs, if there is still a little left, I say just
Embrace it for the unique mojo it brings to this instrument. Then fuhgettuhboutit and enjoy the instrument.
:cool:

Chris_H
09-28-2013, 07:26 AM
yep.. good words.. My personal instruments will never be kept immaculate. Even if I were to be lucky enough to have one of the top built instruments, I would put dents and scratches in it. In a way, the dent matches the mojo of this instrument.. since the inception, the feeling has been Western, range riding cowboy, classy but gritty. I will live.


Thanks for sharing about the idea of Gypsum. I bet the quality of gypsum powder has a lot to do with the clarity of the repair. Gypsum powder from optical purity gypsum would probably be quite clear. I will keep that idea tucked away somewhere for potential use later.

hawaii 50
09-28-2013, 07:40 AM
since it is your personal uke...I guess it is ok to try it...
but if that was going to be for a customer...I hope you would re-do the uke....but I am speaking from the customers point of view...

my 2 cents

Chris_H
09-28-2013, 08:09 AM
I am leaving the dent. If it were for sale, and the repair was absolutely invisible, that might be okay with me. The pieces that I sell are very high end, and I am very, very picky about every detail. Occasionally a small repair in the wood is necessary, and only if it is essentially invisible from a very high standard,. will I let it go out. I stand solidly behind everything that goes out of my shop. I do not want a single unhappy customer, and am doing pretty well with that actually, about 1400 plinths out the door in the last (almost) 10 years.

If I was building this uke for sale, I would likely offer to deliver it, (communicating with the customer first) and tell the customer that an identical (sic) replacement is underway. That way they have something to play, after the wait, and I can take the necessary time to replace it. Yes, IMO, this would be a 'fatal' dent. Actually, any dent would pretty much be 'fatal'. I have had to deal with similar things on a few occasions, with customers. First, I would not let anything that was not worthy leave my shop. I let the customer decide what they want to do. Full refund, replacement, severe price adjustment, etc. Customer comes first always. I have not had to make exception to this rule yet.

Moore Bettah Ukuleles
09-28-2013, 08:35 AM
If you attempt to drop fill with lacquer it's best to let a small amount of lacquer evaporate to the consistency of honey. The solvents in the lacquer will quickly dissolve the base coat and will create a "halo" around the repair when it's cured. You may not notice it for a month or two. Evaporating some of the solvents out of the repair lacquer seems to help reduce this effect. Still, if it's a real dent, the light is going to reflect differently off of it than the surrounding area. The dent may be leveled with lacquer but you'll still see it. Some times you can make a bigger mess of things than trying to fix it. If it's you own uke, let it go. It's how I've gotten every uke I own. Just remember that dents and dings will always occur during the last hour of finishing an uke.

Chris_H
09-28-2013, 08:59 AM
I have learned well that in finishing, anytime you mess with a finish, no matter how small, you are opening Pandora's box... Demons may circle and laugh at you for the most innocent approach.

Beau Hannam Ukuleles
09-28-2013, 11:39 PM
Dame....
This happened to me today on a guitar as i was gluing the bridge on. Ding in the finish with a circular crack. I drop filled it with one, then an hour later a second drop of 50/50 thinners/lacquer (my normal spraying mix)

What Chuck said is absolutely true....always on the day that it would otherwise be finished...........

Timbuck
09-28-2013, 11:55 PM
Best leave it alone ....Look at this :D http://www.youtube.com/watch?v=8mdwAkWvWMw

fromthee2me
09-29-2013, 12:15 AM
Two options I found on YT. Third option is that it gives the instrument character.......

http://www.youtube.com/watch?v=bInx_YOoft4
http://www.youtube.com/watch?v=cdtsa4Sazvw
http://www.wwgoa.com/remove-dents-from-wood-with-a-household-iron/

Let us know how it went.....

Michael N.
09-29-2013, 08:52 AM
I think you are wrong to leave the dent. In fact you should add to them - put a few on the side, Neck and the Back. Then practice and practice until you can make them disappear.
After you've done that you'll be able to confidently call yourself a finish restorer. As a maker that type of skill becomes invaluable.

urcuzzn
09-29-2013, 09:03 AM
my 2 cents,
if the neck is not attached you are free to refinish the top.
get a square of towel 3x3 inches.
use an eye dropper and fill the dent with water several times.
wet the towel, and take out your clothes iron turn on to high.
place the wet towel over the dent and use the tip of the iron on the dent getting in as close as possible.
the dent will steam out like it never happened and u will have to re-seal and topcoat for a perfect repair.

Moore Bettah Ukuleles
09-29-2013, 09:12 AM
Dame....
This happened to me today on a guitar as i was gluing the bridge on. Ding in the finish with a circular crack. I drop filled it with one, then an hour later a second drop of 50/50 thinners/lacquer (my normal spraying mix).

This type of repair always looks pretty good when you're doing it. Let us know how that looks in a week.

Chris_H
09-29-2013, 09:20 AM
I think those are good words Michael, I agree. For now, though, it is a matter of available time. I really want to play this one now. I am absolutely slammed with work, stealing moments to finish the last bits on this instrument. When this one is up and playing, I can unstring my other uke, and fill the holes in the finish that go to bare wood, from when I dropped it in the gravel.

I really would like to hear this one with the finish intact, as intended. I can easily see repairing this dent/finish, and really needing a top coat or 2 to make it fully disappear. I have heard what too much finish does to the sound of an instrument. This time, I get to hear what I built.

Thanks for the encouragement.

There is another experience in being a maker, and that is knowing what the limits of what can be repaired are.

I think the approach I would take on this dent would be to, first try to be able to exactly pinpoint from the inside where the dent is, (there is a sound hole, so there are a couple points of entry. Then using a hot tool with a somewhat fine point and some thermal mass, apply a controlled drop of boiling water to the raw side of the dent. After wetted, I would repeatedly heat the point of the tool in boiling water, and heat the back of the dent. Too much water in the raw wood of the top risks cracking the lacquer, so only one drop of water. Maybe let it sit for a few hours for the water to move into the wood, and then using a piece of 1/8" hard felt, some water, and a fine tipped soldering iron, from the top, being conservative with the heat. This is probably what I would try first. If the finish cracked, then I would use a little less care with the heat, and bring the dent out. Let it fuly dry, and then repair the lacquer. I think with a wood like spruce, 212 degrees is enough.

Beau Hannam Ukuleles
09-29-2013, 02:38 PM
This type of repair always looks pretty good when you're doing it. Let us know how that looks in a week.

Yep......And ive only got 17 days left in oz to finish stuff....
In this case i had to attend to it as the finish had cracked a tiny bit. so it had to be melted back in. Normally i would use our jar of thick finish which is 100% finish that is has been allowed to evaporate- it is really glugy n thick but this doesn't re-melt cracked finish . Ill post a pic in a week.

Chris_H
09-29-2013, 05:00 PM
like diving into icy cold water.....

Beau Hannam Ukuleles
10-09-2013, 03:20 AM
Dame....
This happened to me today on a guitar as i was gluing the bridge on. Ding in the finish with a circular crack. I drop filled it with one, then an hour later a second drop of 50/50 thinners/lacquer (my normal spraying mix)

What Chuck said is absolutely true....always on the day that it would otherwise be finished...........

So I let this sit for as long as I could - almost two weeks then had to level it today before shipping.
I cover the blade with masking tape but it was to thick and I couldn't scrap so it got removed then I scraped down until it looked like in the pic. Then a spot finger sanding with 800, then block sand with 1200, 2000 and buff.

Invisible for now. 5964059641596425964459643

backwoodsmark
03-24-2015, 09:22 PM
hi, I put on a nice tru-oil finish on a parlor guitar I am building. I let the oil cure for a month then started assembly, gluing on the fretboard and bridge. this is when I started getting some small dents in it. then a couple deeper dents appeared out of thin air. I am wondering if some of the techniques that were on utube vids that fromthee2me posted will work? one was using a steam iron on cloth, and one was to put water on the inside of the body under the dent then heating from the outside. I am surprised at how soft this oil is. seems it should be harder unless my oil had gone bad, but it was only 2 weeks old. any ideas on any of this?