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Sinking Paint on Repaired Basses

number six

number six

Jan 29, 2008
451
483
Brisbane, Australia
#1
Hope this is the correct place, I usually only have guitar or amp questions.
A couple of times I've attempted amateur repair jobs on cheaper basses I've bought damaged.
Could be a cymbal stand stabbing, heavy buckle rash or a wayward sharp instrument, whatever.
Not a CA glue drop-fill. A serious gash or hollow.

So I sand it back then use a wood filler (Timbermate here in Australia) and the next day sand it flat.
Rattle can of primer shows it's not as flat as I thought so repeat until the primer looks fine.
Next day, spray some base coat. 2-3 coats, 3 hours apart.
Next day or even 2-3 months later long after final finishing . . . . I can hold the bass up to the light and see a contour of the repair.
Nitro or acrylic, it's happened twice. One bass was fine for 2 months then the haunting came back.
Current acrylic job was overnight and then visible.
It's like the primer is ok but the base coat sinks the filler and primer.
Filler says "non shrinking . . .takes all painting, lacquers . . . "
What am I doing wrong?
Thanks in advance.
 
#3
Wood filler will do that regardless of what the label says, especially in larger areas. Try a good marine epoxy. Not sure what’s available there. In the US I’d recommend West Systems or Total Boat. @Alex Xander may know of a good epoxy available in Australia.

Also, spray cans of finish can experience those issues as well. I understand you probably don’t want to invest but since I got a compressor and spray guns products like Createx Auto Borne Sealer cover and sand and don’t shrink back.
 
#4
Here's an example. J bass control cavity filled with hardwood then topped with wood filler to level. Primer looked fine. I can sand and repeat and it may disappear. Cheap bass, I wouldn't do this to anything resaleable. I've used rattle cans on basses 5-6 times before with no problem but just painting, no wood filler tho'.
I can find PC Marine Epoxy Putty or Loctite Marine Epoxy. Bit Jaco'esque. Fiberglass boats and stuff. If I can't sand this one I'll try that stuff then. Thanks.
Haunted Bass.JPG
 
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#5
Yep, you've discovered shrink-back, which occurs across many materials as they dry. A notable exception is epoxy (and CA glue), but the epoxies you have listed will not really cut the mustard. Those are 'hardware store epoxies' meant for small quantity use, they cure quickly and don't dry glass-hard. They may work for very thin joints, but may also telegraph what's below just as bad. Maybe try a craft store for epoxy resins, they may have something, or a marine supply place will have epoxy, as well as an industrial paint specialist or plastic supplier. West Systems, Total Boat and System Three are names to watch for. The quantity may be large, that's my usual issue, finding small quantities. But the resin will keep while the hardener usually doesn't keep for a long time, maybe a year or two. You'll never look back as you'll never see anything telegraph through the finish again. :thumbsup:
 
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#6
I'll back up what Matt and Beej are saying. Commercial "non-sinking" wood fillers all sink under finishes. They are particularly bad if you are spraying a solvent-based finish like nitro lacquer or acrylic or enamel.

Marine epoxies are the best solution. They don't sink at all, under any finish, even after years of harsh environmental conditions. West Systems, System Three, and Total Boat are the three big names here in the US. I've been using West Systems for over 30 years for restorations and repairs, filling up seams and cracks, It never shrinks or sinks.

If you can't get marine epoxy in your area, the next best thing is the small kits of 24 Hour epoxy, available in hardware stores and hobby shops. Tilt the package, and you'll see that both parts are a liquid, not a paste. The epoxy needs to be low viscosity to go down into the grain of wood.
 
#7
number six said:
Hope this is the correct place, I usually only have guitar or amp questions.
A couple of times I've attempted amateur repair jobs on cheaper basses I've bought damaged.
Could be a cymbal stand stabbing, heavy buckle rash or a wayward sharp instrument, whatever.
Not a CA glue drop-fill. A serious gash or hollow.

So I sand it back then use a wood filler (Timbermate here in Australia) and the next day sand it flat.
Rattle can of primer shows it's not as flat as I thought so repeat until the primer looks fine.
Next day, spray some base coat. 2-3 coats, 3 hours apart.
Next day or even 2-3 months later long after final finishing . . . . I can hold the bass up to the light and see a contour of the repair.
Nitro or acrylic, it's happened twice. One bass was fine for 2 months then the haunting came back.
Current acrylic job was overnight and then visible.
It's like the primer is ok but the base coat sinks the filler and primer.
Filler says "non shrinking . . .takes all painting, lacquers . . . "
What am I doing wrong?
Thanks in advance.
Click to expand...
You can see it, because there's a ridge line between your repair and the hole. Like you said, "...not as flat as I thought..."

You need to over fill, sand completely flat, prime, finish. If you can see it in the primer, repeat the entire process over again until you can't. If you can feel it at all, because your finger don't lie, you'll see it in the finish.
 
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#8
Matt Liebenau said:
Wood filler will do that regardless of what the label says, especially in larger areas. Try a good marine epoxy. Not sure what’s available there. In the US I’d recommend West Systems or Total Boat. @Alex Xander may know of a good epoxy available in Australia.
Click to expand...
I do! Get in touch with the folks at Hammer Roo. Hammerroo.com.au
 
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#11
Just FYI . . .
West Systems 500ml + 100ml hardener $69AUD
SystemThree T-88 236ml (0.5pint US) $85.50AUD
TotalBoat Amazon.com.au 0.5 pint US) $174.55AUD
Hammerroo Rapid Cure 500ml $88AUD
BoteCote 150ml sample kit $20AUD but is it any good?
I'll try sanding and priming first and then if no good it looks like the West Systems (which is also closest).
Lots of options so thank you all!
 
#12
number six said:
Just FYI . . .
West Systems 500ml + 100ml hardener $69AUD
SystemThree T-88 236ml (0.5pint US) $85.50AUD
TotalBoat Amazon.com.au 0.5 pint US) $174.55AUD
Hammerroo Rapid Cure 500ml $88AUD
BoteCote 150ml sample kit $20AUD but is it any good?
I'll try sanding and priming first and then if no good it looks like the West Systems (which is also closest).
Lots of options so thank you all!
Click to expand...

I knew there would be marine epoxy in Oz. I personally recommend West Systems. What you want is the 105 Resin and the 206 Slow Hardener.
 
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#14
billdylan said:
Would a skim of Car Filler or builders bog be any good and not shrink ?.Just wondering as Epoxy is pretty expensive if you are working to a budget
Click to expand...
In my own experience, they all shrink back. I've tried all measures of grain filling, and only the resin-based methods will retain their dimensional structure over time. I'd rather work with epoxy at home than polyester, though I have it too for my wooden boat. Fast-drying epoxies remain too soft in my opinion, and for anything that will form a substrate, I like a slow cure for better hardness. :thumbsup:
 
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#15
About 10 years ago I tried that resin stuff people coat trays and tables with that self-levels. 2-part clear with a glass finish. That worked for 3 months before I could see the contour of the mend. CA worked for small chips and fretless necks. Not tried boat epoxy yet. You wouldn't want that to shrink out at sea . . .
 

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