Yet another mess-up

ChuckBarnett

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I'm not even going to mention all the feelings I have experienced the past day or so. I'm humbling myself again to ask for help. Please tell me it gets better.

I was excited that the uke is in the finishing stage. I had bought and applied 3 coats of Aqua Coat as a pore-filler (with little understanding of what that even means or looks like). Looked good to me. Somebody said use a foam brush to apply Tru-Oil. I watched a video where Robbie O'Brien said "wipe it on and get away from it". Then watched one, suggested here, by somebody who makes Mye Moa ukuleles. That was very helpful and it was then that I realized that the end goal drives your choices about how to apply Tru-Oil. Glossy versus not glossy. That may explain the differences.
I did 3 coats of Aqua Coat because that's what I saw on a video, again, not realizing that Koa isn't the same as Rosewood. (I have since learned that it's one of the species with the biggest pores!) I showed the instrument to a guy locally who observed that it didn't look like it was pore-filled. He then showed me a couple of his guitars and then I could see the purpose of pore-filling. I realized that I could have put any number of coats of Aqua Coat and not stopped with 3. But, again, it looked good to me... (not having any clue what I was doing).
I slathered on 3 coats of the Tru-Oil and thinking that I had adequate"build" so as to "level sand" which I did.
Things were still going okay I thought. I spotted a horizontal line, somewhat of a low spot about and inch or so long and decided to take care of it at this early point. Used a scraper and then 0000 steel wool. Hit it with a coat of Tru-Oil and then 2 more, all 3 were rubbed in more like French polish, which was what I did on my other uke successfully.
From the photos you can see the color difference compared to the surrounding area. You might also see that I've successfully removed a LOT of wood! And perhaps you can see that there are still imperfections in the wood. Different ones that weren't there earlier.
Is the fact that I've blown through the layer that had the Aqua Coat to reason for the difference in color and the lack of any glossiness at all?
Can I take the whole top down with a random orbital sander and start over? At the least, can I sand to blend in that low area with adjacent areas?
When I'm done with this, I'm going to compile a list of the things I have redone. There are mistakes from my first one I didn't make this time; no need -I made plenty of new ones!

I take up way too much time with my stuff on this forum. Apologies!
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That's a nice instrument! I like the purfling. I'm a sucker for abalone. If it's any consolation, I built my first instrument (an electric uke no less) in 1999 and I'm still making mistakes more than 20 years later. It's just part of the hobby. So don't be hard on yourself.

Also realize that there are differing versions of success. Especially with finishing techniques. Some people like a totally smooth pore filled glossy finish and others like a thinner looking more natural finish where the pores show through. There's really no right or wrong, and while there are a dizzying number of variables it's really about finding what look you like and then how you can get there.

Which brings up probably the most important tool in your finishing arsenal. Practice. Get your hands on some wood scraps - cutoffs from your build - and finish them! Do this over and over until you're comfortable with what you can accomplish. You can even "damage" one of your test pieces if you want practice repairing. When I try a new finish technique I may do half a dozen tests or more before I touch a "real" project. It seems like a lot of time to invest but it's a good way to reduce variables and end up with a known result.

For your uke - you may be able to sand out that spot and refinish it. Tru oil blends into itself nicely. It's hard to comment on why it's darker but it may be because you sanded through the aqua coat, which was sealing the wood and preventing the tru oil from sinking right in. Tru oil has an amber tint (pretty much all oil finishes do) and if it soaks in more it'll get darker. So if I were you I would GENTLY sand just that area with fine sandpaper until you removed the discoloration and then start over with the aquacoat and top it with tru oil.

Any time you're sanding, buffing, polishing on a finish you need to train yourself that less is more. You can always sand more but you can't sand less! Train yourself to use finer sandpaper than you think and to stop prior to when you think you are done. Pause, look over your work, hold it up to the light and check for scratches or imperfections. Make sure you're aware and informed of what you're doing and slow down if you're not.
 
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What it looks like to me is that you have created a concavity there over the tail block. Sanding and then trying to match up that part of the finish with the other parts is gonna be tough. The nice thing about finishing (if there is a nice part) is that you can take it all off and start over. The overall finish does not look good to me anyway and if it was me I would take it off on the entire top with an orbital sander going back to near bare wood and start the process over again. Hey, it happens.

As for pore filling it does take experience. When you are sanding back look for little shiny spots. These are the pockets which have not been filled yet. Pore fill, sand until you get an overall dull look. This means you have reached a "level sand" and your pores are filled. As you get experience you will be able to spot those little shiny things.

Good luck!

Old saying: "Finishing is the Achilles heal of lutherie"
 
I'm going to throw this out here even though it may not be directly pertinent to your problem. Someone might do search for AquaCoat and koa, find this, and be saved from disaster.

NEVER use AquaCoat over raw koa. Sometimes, but not always, AquaCoat causes koa (and its near cousin, Tasmanian blackwood) to discolor with a greenish cast. That can be a big problem. Apparently, this is a potential issue with any water-based product and has been reported on various lutherie forums. To pore fill koa, use epoxy or CA or something else that doesn't have water in it. Also, don't use a water-based sealer or finish over raw koa. At a minimum, seal first with two or three wash coats of wax-free shellac.
 
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I appreciate the graciousness of you folks toward me! Very much!

I did try to level that up best I could and I think it's not bad. I'm a little concerned because I'm not sure if I'm into that Walnut end block or not but I stopped quickly as I realized something was not quite right. At this point I'm happy just a button it up and move on in life. You learn from your mistakes and some of them stand as reminders every time you look at something, no?

Now to do the pore-fill again. But because of the concern about Aqua Coat and Koa, although I saw none of that my first go-around with this uke, I'm prepared to do yet something else. I know that a number of you do the CA glue trick for pore-fill. I watched Beau Hanam's short video on pore-filling Koa and best I can see he used medium CA glue and simply rubbed it on in swirls and then straight strokes to end. He did a small section at a time. I don't know how you avoid the rag sticking to the wood but I'm sure I will pull up if that starts happening. Any tips?

And, yes, I will be practicing on something!
 
I have found aqua coat to be a terrible pore filler. The only way I have used it successfully is to pore fill about half way through a lacquer finish when you have enough coats on so you don't sand back through and the lacquer has reduced the size of the pores. I find CA and epoxy both superior. I'm also wondering if you sanded back to bare wood after you pore filled or left a thin coat of aqua coat on the entire surface. That's something I would not do. I would rather have a coat of shellac on bare wood or epoxy.

To answer your question. If you don't have top too thin issues of course you can sand back with random orbit or by hand.
 
Michael, I have no idea how to tell if I've sanded all of the Aqua Coat. This whole thing is a mystery to me. I see under magnification things that I assume are pores in the wood that have something in them. I assume that is the Aqua Coat. But the surface pretty much seems to have been sanded down to bare wood.
 
If you are lookig to get a blemish free (no pores showing in finish) then by far and away the best option is an Epoxy pore fill. You can do similar with CA but I've found it still moves around a bit and shows through as the instrument ages. In either case before you move on to finishing, the surface of the timber has to be as perfect as you expect your finish. Especially if you are going to use something like Tru-Oil which has very minimal build and pretty much nothing in the way of being able to level sand and buff like other finished do.

On Australian Blackwood, which is very closely related to Koa, I apply in 3 sessions of my Epoxy (Bote Cote) with 24 hours cure between each session. Sanded back with P240 grit dry paper between each coat. Then there is a catalyzed sanding sealer finish applied. Overnight cure and then sand out to P240. Then 2 sessions of catalyzed clear coat. 4 coats each session with a 24 hour cure between. The first session is level sanded 24 hours and the second session applied. That one cures for a few days and wet sanded out to P2000 and final buff.

You can see that finish on the Blackwood Soprano I just posted here.
 
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That is great information, Allen! I may experiment with epoxy soon.

Beautiful instrument, by the way. I love the wood!

I've seen this description several times, that if you want a blemish free finish...no pores showing... I wonder if there's anybody out there who can provide me a couple of photos comparing pores showing and no pores showing because I don't know what that means. If it means that there are no tiny dips in the surface of the finish, can't that be fixed by building enough finish and sanding back so that all is level? If it means you cannot see the pores through the finish, that makes no sense to me. My only experience was building a tenor with quilted Maple sides and back and a redwood top. The finish turned out decent for a first instrument. Everything I read says Maple doesn't have big pores so I didn't have to worry about pore-filling. (Having zero experience with woodworking has not helped me with building instruments.)

Gratefully,
 
How many coats of CA glue does one use for Koa? Do you sand between coats? Waiting time between coats?

Thanks

Number of coats - until the pores are filled to your liking. At a minimum aim for uniformity, it's easy to have the first few coats end up patchy since it doesn't absorb consistently.

Drying time is often very quick - ten minutes maybe. Longer if you're applying a lot. You'll know when it's set up by the look/feel.

The trick to not sticking your cloth to the uke is to have enough CA that it can't cure quickly enough to stick. The more CA on the surface the longer it takes to cure.

I'm sure this is obvious, but wear gloves and wear a good respirator. CA in larger quantities gives off a LOT of very noxious fumes.
 
Michael, I have seen calipers that can be used to determine thickness through a sound hole. Seems they are a pricey investment, but at this rate I may need one. Otherwise I am only guessing about thickness of the top.
 
If it means that there are no tiny dips in the surface of the finish, can't that be fixed by building enough finish and sanding back so that all is level?

Yes, technically that is true. But the problem is that you would need many, many, many coats of finish to accomplish that. CA or epoxy is quicker because it gives a thicker build on the wood which can then be knocked back. Here is one way to visualize pore filling: Think about if you dug 2 foot holes in your backyard and then brought in dirt and covered the yard 6 inches deep and then scraped off all the dirt. The holes are now a foot and half deep. Then you added 6 inches of dirt and scraped that off. Now the holes would be 1 foot deep. You get the picture. You would have to be putting on enough dirt and scraping it off to fill the holes until your backyard is level.
 
Thanks, Sequoia. That is an illustration that makes perfect sense. So the pore-filler saves time down the road possibly. Can you use enough applications of other pore-fillers like the aqua coat for example and accomplish the same goal?
 
Hi Chuck, the problem with Aquacoat is that is shrinks back and never seems to fill pores fully, as you've no doubt found out for yourself by now. I have a tub of it and I've tried it a few times, the last time I gave it 4 coats, which initially looked good but once the finish was applied, the pores were still there for all to see. I think I've given up with it now, and only use epoxy from now on. Epoxy is messy to apply but it works.
If you continue to experiment with aquacoat, and apply more coats, I would suggest you give it a couple of days to dry before deciding what to do next and hopefully any shrinking has finished by then.
 
I’ve used a CA pore fuller for almost 15 years with excellent results. I have seen absolutely no shrink back on instruments that old. I prefer it over epoxy because I can apply and sand 3 coats in little more than an hour. CA pore filling is not for the faint of heart. As mentioned before, good ventilation is a must. I apply it outdoors, with a mask AND a fan blowing fumes away from me. It’s also very difficult to to correct runs or drips so you have to work fast and cleanly with confidence.
I’ve written up a handout that I’ve given to many builders throughout the years. If anyone is interested, email me at moorebettahukes@aol.com.
(Chuck, I believe I’ve already shared this with you.)
 
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