Thread: Ktm-9

A number of small shop luthiers in the US use the stuff, but if you're going to spray it, you'd better still have a real spray booth. The stuff may not be "toxic", but overspray of any kind is not good to breathe.

My personal experience with waterborne finishes is that the main ingredient seems to be wishful thinking. I've not yet seen a waterborne that can hold a candle (as it were) to nitro lacquer which is itself a highly flawed finish medium. The waterbornes tend to be soft, take imprints all to easily and are very sensitive to marring; they take a long time to cure, and you'd better do a great job pore filling if you don't want to see a tremendous amount of shrinkage in six months to a year. Check out the thread on waterbornes at the "OLF" http://luthiersforum.3element.com/fo...14480#forumTop

We'd love for this stuff to be the "silver bullet"...but it's not.

Best case...do a great job pore filling with epoxy, then sealing with good old shellac, then use as little waterborne lacquer for top coats as possible...and it still won't look as good as a decent nitro job or a thin poly finish.

Consider French polishing over epoxy pore filler...or buck up and do it right with nitro or poly.

mmm
i gotta disagree here
you need proper pore filling with any kind of finish
i seen plenty of guys who just shoot nitro till they can level it
to me thats a lazy way of surface prepping
i found WB lacquers pretty easy to use and with decent surface prep and properly cured they look every bit as good as nitro.
the pros for using WB lacquer:
great looking finish and tough
no risk of explosions while spraying a job
no approved spray booth required
no splitting and crazing when the guitar gets very cold
clean up with water
no bloom when spraying while cold or humid
your neighbours wont complain
you won't rot you guts out breathing in the fumes

i know a lot of people use it but i wont use a product that impacts so much on my local envronment. if you are building guitars in a backyard workshop its a way cheaper and cleaner method to us WB lacquer. if you asre in a factory you'll save thousands on setting up the booth.

in many shires if you get caught spraying nitro without an approved spray booth you are in big $$ trouble. - it only takes 1 neighbour to complain

I trialled it for a while, and went back to Nitro. It works similar to nitro, dries similarly, and buffs out reasonably. I think i can get more shine from nitro, and nitro adds a nice amber 'warmth' rather than the (to me at least) un-natural hue the KTM9 leaves. I did have one trial bloom, but i was testing the extremes of the product.
I usually try to keep some in stock, because it seems to be popular amongst certain people. Its more costly than nitro.

(when referring to nitro, i mean the REAL stuff, not the pre-cat rubbish they pass off as nitro that can be buffed within days)

If you are going to use the stuff, I'd go with Old Picker's advice on surface prep being the key. You should consider epoxy pore filling first...then do a good shellac seal and get it really flat sanding to about 320. Do two or three coats if need be, but don't burn through the last coat before you go to the WB lacquer. You want to put as little WB on top as possible understanding that it is not for filling pores, gaps, dings, or whatever; it's just your top coat that will be final levelled and buffed.

There are a lot of reports in the 'States of WB coming out looking fine at first, and then getting rough, pitted, and pebbly after about six months. Both Mike Doolin and Charles Fox (incredible builders...) were initially enthusiastic about KTM9, and now Mike has switched over to polyester and Charles back to nitro.

I have found that even after two or three weeks of cure, the WB that I tried (Crystalac) imprinted terrible left over night on my work bench pads, it scratched too easily, and in the end my customers just hated it.

I'm open to improvements, but I'd not try it again without doing all the surface prep and sealing I mentioned above, and in the end it may just be easier and better to go with a good short-oil varnish for a finish one can do without a spray booth.

Thanks for the replies.

I'm planning on restoring an old Strat body. I'd like to finish it in a solid colour.

I don't want to use spray equipment.

What would people recommend?

Cheers,

Chris

Originally Posted by Rick Turner

I'm open to improvements, but I'd not try it again without doing all the surface prep and sealing I mentioned above, and in the end it may just be easier and better to go with a good short-oil varnish for a finish one can do without a spray booth.

i am using colortone from stewmac and had guitars with me for 12mths playing and not noticed any problems with the finish. I did have one that crazed badly in one spot but that was due to overheating the surface when i leant in too hard for too long when i buffed it out. when i went back the next day one spot the size of my hand had crazed but in 18 mths it never travelled 1mm. i learnt with this stuff and i have gotten used to how it works and for me anyhow i have no problems with it...

a solid colour finish will be especially challenging by brushing
don't use enamel paint

"Old Strat body"... How old? Pre-CBS? Take care; you can ruin the value of old Strats by refinishing them if they are of particularly collectible vintage. On the other hand it's your guitar!

It's a mid-80's model and it's already been stripped back to the wood so the damage is done

Are there any other makers of water borne lacquers (other tha KTM-9) that people would recommend? Also epoxy fillers? I am interested in what people might use and recommend.

Cheers,

Peter

I'm using WEST Syestems epoxies which were developed initially for the wooden boat building crowd. I don't know if these adhesives are available in Australia, but you do have a very active sailing scene, so I'd think that equivalents should be there. WEST has a very full range of epoxies, hardeners, fillers, and very convenient metered pumps for dispensing the correct ratios. For pore filling, we brush the stuff on (it's fairly thin), slowly squeegee it off at about a 45 degree angle to the grain, let it harden, and then sand it back to bare wood, taking care not to go too far. You want to leave the epoxy just in the pores. Once or twice with that, then we pre-seal with Waterlox, a tung oil product, let that dry overnight, and then proceed with a normal finish schedule. Ours is with a urethane sealer and then polyester top coats, but you could do anything over the epoxy/tung oil. You don't want to leave any tung oil on the surface; it's mainly just to wet the wood to the same degree that the epoxy did, and it also acts as a "tie coat", helping to adhere subsequent coats of finish to the wood.

By the time we start spraying, the surface is very, very flat. All pores, dings, and gaps are 90% filled, and this preparation helps to minimize the number of coats required to build finish, and it also prevents any sinking back of the finish into the pores. In the end we get a very thin, very flat, very durable finish.

Solid colors get done between days of spraying polyester and are done with urethanes.

i use timbermate woodfiller mixed down to a slurry
cheap, buy it at bunnies, no nasty chemicals, if it sets you can rewet it
a couple goes with that over a thin wash coat of shellac or lacquer and your done.

dont sand it back too hard and use a flat, hard sanding block with 320 or 400

Zpoxy is a local product the accoustic makers use

btw what happened to those dudes [kiwigeo & co] who used to hang out here??

I have to say, it cracks me up to be identified as "an apprentice" on the forum here. I apprenticed as a luthier in 1963...yeah, 44 years ago...

Hey Rick, I had a chuckle at that "apprentice" bit being applied to yourself, too. You can customise it in the User Profile options.

West Systems is batched locally, not sure of the base stock origin but it comes from a company in Queensland called ATL Composites. Have used it myself for years, mostly on bass fingerboards.

Stuff like it, or nitro for that matter, is nowhere near so readily available here and everything is dearer than you're used to. Even the local hardware chain is a weak copy of Home Despot. Thought I should raise this issue in case you'd assumed that certain supplies for your course would be dead easy to track down...

Cheers, Adam.

Thanks, Adam...duly noted.

I'm going to be sending over most of the supplies needed to build the mandolins, but I'm also going to set up a small workshop at my girlfriend's place outside of Hobart with the idea of trying to make more of the parts in Tasmania with local timbers as much as is practical.

Is there a decent tung oil product you can recommend in Australia?

This probably starts another thread, but what the heck...