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I built a guitar last year and used Ktm9....I used Z-Poxy as a pore filler did a couple coats of Shellac and brushed on the Ktm9.(around 12 coats)..The body came out looking ok but the neck is showing some wear in finish...Its rough and looks like there is small pores...I now have a spray booth set up and want to refinish the neck...Should I removed the finish down to the bare wood or use a 400 gr sandpaper to scuff up the neck and respray? TKS

What are you looking to re-finish with? 400 grit does not provide enough anchor for most finishes.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Thanks for replying Brian. I will be using Ktm9 again, only spraying it on this time. Do you know if using the correct grit of sandpaper can give me enough of an änchor" to refinish with a spray or is it better to remove the existing finish and start over.....

You should be able to sand it smooth with 240 and reshoot. But I'd skip the KTM-9 and use something else like their SV. There's a good chance that what is happening now will just happen again with the 9...

Yeah...that makes sense....The only other waterbased lacquer I have on hand is EM7000HBL..Would they be compatable?...The only problem I have with the Em7000 is the blue tint....

I can only speculate about compatability, but I think they're both acrylics so should be ok. But it is only speculation. To be safe, I'd sand, shellac, scuff, respray...

I would not go any finer than 220 grit, 180 would most likely be my choice. No matter what finish you put on top now you risk delamination if it can't hold onto the existing finish. The problem you have was most likely caused by improper conditions during initial drying or the coating being applied to thick. The surface dried before the rest of the coating leaving small pockets of air/gas trapped in the coating.

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

You might want to consider sanding to bare wood, sealing with shellac to isolate any Z-Poxy remaining, and finishing with a non-waterbased material. I've used KTM-9, Target USL and EM6000 on necks in the past and they all broke down eventually. Have not tried 7000 or SV. I kind of decided that waterbased + neck = bad idea.

Tru-Oil is a nice neck finish but Z-Poxy beneath will cause it to get "fuzzy" so some sort of seal coat is needed if there is any residual Z-Poxy.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Don't give up wb until you've tried SV Terrence.
I have a personal guitar with it that's stood up as well as any other finish, and I have chemistry that eats the KTM-9. It's a different material than the KTM-9.

Thanks, that's good to know, I probably will try it.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I too have had a similar problem on a neck. Although I usually use KIM 9 on my guitars with no problem, I used tru-oil on this one. I put over zpoxy, a couple of years latter the zpoxy started coming out of the pores leaving it ruff. This was happening in the areas the that I held the neck the most.

I kind of came to the conclusion that its was not the tru oil or Zpoxy. It was the way I put the zpoxy on. just for the NECk I thinned it quite a bit with Denatured alcohol. it did go on really easy and appear to fill the pores just fine. but I think that was why it came out.

I sanded the neck to bare wood , reapplied full strength zpoxy and sprayed it with KTM 9 . it came out fine and has been no problem since

Thanks for the info...I applied this finish with a roller and there were lots of small bubbles..I used a small foam brush to level out the finish and remove the bubbles...i am thinking Brian may have hit the nail on the head with bubbles being sealed in the finish...I have the neck sanded back to bare wood and will try spraying it on this time....cheers

I've been using KTM-9 on all my recent builds - often over Zpoxy - and have had absolutely no problems. One little trick I learned is to spray a mist of denatured alcohol between coats (or on your old finish) right before the KTM. I clean my gun with water, then put a little DA in the cup and shoot that to clean the water out, leaving it in the cup. After sanding and preping for the next coat (220 or 320) I just mist the DA, dump the rest out, put the KTM in and shoot. The DA will slightly tack the old finish and the coats seam to melt together.

I had some witness lines with other water based lacquers, but never with the KTM-9.