Residues in cracks

[blackrock]

Hi
I'm pretty sure I've probably messed up already, but thought I'd impose upon your knowledge and experience.

One of my Ricks is a '78 Burgundy 4001 which I thought I'd spruce up. I'd already straightened bent truss rod ends and replaced the little aluminium truss bar with a robust 3/8" square brass one. Incidentally, for anyone struggling to get similarly downward bent rod ends to lift up over the truss rod recess edge and out of the neck, I found that using a plastic poster hanger makes a great guide channel to feed the rod through, then you can easily slide the rods out and in of the neck and also prevents any damage to the finish on the edge of the truss rod recess.
I also G-clamped out a little tailpiece lift using the method described in another thread (thank you), and was puzzled to discover there was still a gap?! On investigation I found that the body itself wasn't flat. Makes me wonder if a lot of people's concerns about tail-lift is actually always that.

Anyway, on to my current problem. I'd read several threads here regarding the Scratch-X/Zymol treatment, so went ahead and bought these (I'm in Scotland, so can still buy Scratch-X version 1).
The finish was still perfect in the summer, but when I looked it out few days ago to begin the 'spruce up' the entire lower half on the back of the bass looked and felt to me similar to someone having dragged a big paintbrush over the finish while it was still wet (although the finish itself was still hard). The finish everywhere else on the bass is fine and my '75 4000 fireglo sitting next to it, also fine. I assumed I must have wiped the bass in the summer in this area with a cloth contaminated with something which reacted with the finish. Hoping it was purely still superficial, which I could cut back, I sanded it with 1500 wet and dry.

Ooops! Yep. things are certainly flatter now, but many of the 'brush marks' are now white and looking closely, they are actually extremely fine cracks filled now with unbudging sanding residue. I now realise this was in fact oddly localised crazing/checking which I now assume now somehow happened because of this very harsh winter (it's been in the same room the whole time without any temperature change though).

So, I've now a bass with the back lower half looking hellish - matte and hazed from sanding and with currently unmovable fine white sanding residue filled fine cracks. Where do I go now?
A refinish is out (I was recently made redundant). Seems to me whatever I do, I'm still going to need to use Scratch-X to get rid of the sanding matte/scratching and match it to the untouched top half of the back anyway, I expect leading to yet more white residue in the fine cracks.

Any tricks to visually reduce the whiteness of residues in fine cracks?
Would flooding with thinned down clear nail polish fill them a bit and allow a light resand/Scratch-X/Zymol? I only mention that as I notice the residues seem to 'disappear' when wet - so trying some lateral thinking (or should that be stupidity?) Would that even work? Even if it did, would such a 'bodge' potentially later lead to further problems?

Or given the stage I'm at, do I just go ahead and Scratch-X then Zymol and accept the resulting white residues?

Sorry about the long post, I'd appreciate any advice.

[doctorwho]

Welcome, Tschick.

No problem with a long post being that you have detailed the problem(s) very well.

I am not a luthier, so I can't provide any advice, but if you could take some digital pictures and post them, that might be useful for the luthiers to advise a course of action.

[jingle_jangle]

Hi, Tschick-

Photos, as Gary has suggested, would help, but a history of the bass is more helpful, as I'm at a loss at this stage to understand exactly how this happened to the back of the bass, before you began to sand in order to level the back.

Original RIC conversion varnish will take some sanding and then buff back well. If the bass has received a touch-up at some time in the past, you could be looking at a different finish in that area. There are a number of scenarios that could also be true, but in cases like this, often photos won't tell the story, either.

I would not flood the area with thinned nail polish. This is merely compounding the problem. At least a partial refinish would seem to be called for, so leave it alone until you can afford to do so.

[blackrock]

Thanks for the feedback guys. I struggled getting representative photos, but hopefully these might be a little help all the same. The close up is more how things look in reality if the light noticably hits the cracks and the wider shot gives perhaps an idea of the area and crack pattern (actually many more finer cracks that the camera hasn't picked up but on the other hand the flash makes the white looks probably more noticable than in reality).

As far as the history of the bass goes, it's a '78 which I bought virtually unused from the original owner around 1981 (the father bought it for his son, but the lad wasn't interested in learning to play and ignored it, so the father sold it to me). So I can confirm everything is original with no refinishing ever having occured.
I gigged with it for around 12 years and since then it's sat in a cupboard in the unheated spare room in a soft gig bag. I had visitors coming in the summer, so had to clear out and decorate the room, (when I fixed a damp issue I found in another corner of the room incidentally). At that time I checked my basses - the 4001 was still perfect, but if I remember correctly may have had mild, barely perceptible damp bloom in places. Anyway, I wiped that off with plain water (I had been using cloths with distilled white vinegar to wipe any bloom on anything I found in the room, so possibly may have used a cloth 'contaminated' with vinegar - if that's an issue?). So, all looked pristine again and I believed I'd now fixed any damp issues in the room, so the bass went back into the gig bag in the room cupboard.
Damp still seems gone, but we had and extremely cold and prolonged winter with the room remaining unheated. I looked out the basses a few days ago for the shine up and found the issue - still in the cold room though, so no temperature change. By the way, the bass stands upright in it's gig bag and I also found slight rust pitting now appearing on the tailpiece which wasn't there before either. So can it just have been the cold and damp? Odd to me though, why it suddenly happens now after sitting in the same conditions since I stopped gigging 15 or whatever years ago and being unchanged all that time.

I had a think about your mention of a possible partial refinish solution Paul. Hmmm... in some ways, if push came to shove, I think I might prefer the idea of retaining it's originality from my gigging days (maybe over-riding a desire for a refinished pristine look). If I went for an alternative attitude adjustment of just accepting the white then, and ploughed on with the Scratch-X/Zymol would this lead to seeping under and finish shedding?

[jingle_jangle]

Those photos are pretty telling. I somehow was under the impression that this was checking of the finish.

Instead, what I'm seeing is wood that soaked up a lot of moisture at one time and is only now showing the results. This type of with-the-grain cracking through the finish shows two things--an expansion/contraction cycle in one direction--indicative of moisture absorption--and the subsequent splitting of the finish that happens when it's stretched beyond its capacity along the grain.

Additionally, it's impossible to say when the water absorption happened, but the cdombination of the absoerption and drying cycle(s) are what caused this.

Let it be for now, and if it continues to bug you, get a partial refinish sometime later.

[blackrock]

I daresay it was my rambling and stabs in the dark that gave the impression it was checking. Your explanation also helps me understand why there was so much over a continuous area on the back though, Paul.

I'm glad Gary prompted me to put up some pics now.
Having owned it for the past 30 odd years virtually from new, I was always fairly good about taking reasonable care of it such as wiping down after gigs etc - don't recall any abnormal wetting dramas.

So... just a theory based on your information - maybe sitting in a padded gig bag in that spare room with the damp issue in the opposite corner is where it gradually absorbed the moisture from the air in recent years. I come along and fix the damp corner a couple of months ago, dried the air out and then contraction occurs. Could it be? Might explain why it still all looked perfect last summer before I fixed the damp in the room. Be kinda ironic if it was caused by me trying to fix it's living conditions.

Anyway, (assuming my pet thoery isn't way off beam), I suppose I should be thankful it's just occurred in the one area on this bass, or hasn't happened to my other basses which were beside it ...yet? - (I'm hoping maybe the hard cases they were in helped protect them a little, if the damp was the cause).

Well, it's gonna require all my concentrated patience not to touch it and let it be for now (I was really itching to get Zymolling too).

Thanks Paul, I really appreciate your time and expertise here.