Official Luthiers Forum!

having finished my first 2 guitars by French Polishing I decided to invest in some spray equipment. This got decent reviews :

http://www.earlex.co.uk/professional-hv5000.html

There is no way I can set up a booth in my shop for nitro so water based seemed the way to go, KTM-9 to be specific. This is where I need some (lots) of help. I've read everything there is to read on water based finishing, spraying etc etc and all seemed ok after the first couple of coats (I did a lot of test spraying beforehand). However ... I have a bit of a problem (to say the least). Firstly I got loads of orange peel and unevenness. I shot 4 coats on the first day at a temp of about 20deg and rh about 50, misted with denatured alcohol on the second and a further 4 coats. The coats were completely dry between spraying sessions. I've read that its always a bit uneven and "orange peely" straight out of the gun so today I started sanding with 1000 grit wet and dry thinking that'd even things out. All thats happened is that small shiny dots of the finish appear and I think I'm back to bare wood (I find it very difficult to tell when you're back to bare wood by the way). The guitar was pore filled with Z-Poxy and nicely smooth before spraying.

So ... helppppp lol. I dunno if I'm spraying too thin a coat or too thick a coat (I did have some runs that I had to remove with a finger) or if its "normal" to have this orange peel. I also have maybe a third of a quart tin left after 8 or so coats and apparently a quart tin will finish 6 or so instruments?!

Now I think I'll have to sand the whole guitar back to bare wood

If anyone else uses this Earlex some idea of gun settings would be great too

Thanks all for any help/advice/wisdom!

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imagination is more important than knowledge, knowledge is limited, imagination encircles the world

I think you would see if you were back to bare wood. Sand back one of your test panels to see what it looks like if you need to. If the orange peel is heavy as you say then you need to start with a much coarser paper and work your way up through the grits, 320 or 400 would be a good start. the shiny spots you see are the low spots in the orange peel, they stay shiny until they are scuffed. Sand until they are about 75% gone with the 400 and then start working your way up 600, 800, etc. by the time you get to 1000 or 1200 the surface should look completely dull. Now it is ready to be buffed.

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Brian

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

https://www.howardguitarsdelaware.com/

many thanks Brian. When you say 320 grit .. I think that means about P400 here in Europe? :

http://www.mibnet.se/home-improvement/s ... dards.html

so basically when shooting water based its a matter of getting enough coats on there (as evenly as possible obviously) to be able to level sand before buffing? I'm thinking maybe my coats were too thin and I've sanded through. If the shiny spots remaining are the low spots then presumably the duller surrounding area is just sanded finish and not wood? (providing the pores are filled - but I have this on the soundboard too). Also when spraying the KTM-9 - should the coat look glossy for each pass? I've read on StewMacs site that for EM7000 the coat should basically look almost matt with no gloss. Confusing to a rank amateur like me

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imagination is more important than knowledge, knowledge is limited, imagination encircles the world

Abrasive Grit equivalents - may be useful to you.
http://www.fine-tools.com/G10019.htm
I feel a bit awkward offering advice, as I am just about to start spraying waterbased for the first time (although I used to spray industrial paints for a living some years ago) but have been researching it on the net (heaps)
What size gun tip are you using - if using a standard needle/tip it is 2.0mm, a smaller one may give a better finish of the gun, 1.5mm (& 1.0mm) are available.
Also with waterbased, many people commented solids tend to build up at the tip causing splatter, but you have probably noticed that.
Anyway, wish you luck and success.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Hi
I use the same Earlex as you. I've sprayed about 5 instruments with it and have had excellent results - even as a newbie! I don't know anything about spraying KTM9 but I am spraying EM6000 which is also a waterborne finish. I am in England (I see you are in France) so I have to get the finish direct from Target Coatings. This makes the shipping really expensive but to be honest I have had such great results that it is worth the extra expense.
I have managed to get what I think is a good thin flow from the spray gun (I've never measured the final finish thickness but it feels good and thin). I only dial the spray gun's open/shut valve about just over half a turn from the closed position. It really is only just over half a turn but I get a really good coat which is not too thick but gives good coverage. I get some orange peel but nothing major at all.
I spray 12 -15 coats. Sometimes I scuff/level sand in between coats but only after a session (every 3 or 4 coats).
P400 is too aggressive. I level with p800. I find it useful to give a good level sand before I spray the final few coats. If I do a good enough job I will level sand with P1000 after the final coats.
I use Z-Poxy but I also put a seal coat of shellac on top before spraying. I don't know if there are issues with KTM9 over Zpoxy?
As an amateur builder I find the Earlex to be a great piece of kit and it gives pretty professional results. You should persevere as it will work for you when you get more experience with it.
Mat

thanks Colin - would you believe my local hardware place only carries paper to P240? Looks like I'll have to order even my sandpaper off the net

Yeah, the tip does clog after waiting between coats a bit but I just nipped that bit off and all was fine. I may well try a smaller tip as well. I actually took it back to wood and played more with the gun, then used a much finer setting and got a nice result. I dont know if it made any difference but I read that its better not leaving the guitar hanging vertically after a spray so I did the back, left that to dry horizontally then the front etc etc .... not much orange peel or unevenness at all so all seems good

Hi Mat - the Earlex is a fantastic bit of kit I agree. How did you manage to order the EM6000 from Target Coatings site? When I tried it didn't give me any country option for delivery except the USA at checkout. I'd like to try that for the next, unless of course you can spray EM6000 over KTM-9. Thanks for the advice re the gun, thats just what I was looking for. My second attempt was with it dialled just about where you say and the result is way better. I have a feeling I was somewhat "heavy handed" with my first

As far as I know KTM-9 only has issues when used over oils, all is fine with shellac or Z-Poxy. My next will be with clear Crystallac which looks like a nice way to pore fill (if there ever can be a "nice way" to do that lol)

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imagination is more important than knowledge, knowledge is limited, imagination encircles the world

Good to hear things are getting better Rick.
BTW - Crystallac- have you got a source for that on this side of the pond?
I'm going with Z-poxy for this one, but have tried to source Crystallac to try hereabouts with no success.
Matthew, I had a look at your posts and that's a lovely finish on your EM 6000 guitars.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I got mine delivered to a friend in New York then he sent it to me .... I did find what I think is the same thing here :

http://www.easupplies.com/CRYSTALAC-CLV ... ad126j.htm

but I played it safe and got the one from Rockler in the USA. I think thats the same stuff in that link though

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imagination is more important than knowledge, knowledge is limited, imagination encircles the world

Rick - I may have phoned them at Target but I probably just emailed them. They were happy enough to send the finish to England. I bought two gallons as that made the most sense until I realised that the finish only has a 6 month shelf life . I used it anyway and didn't have any problems.

Colin - Thanks. Buying the Stewmac buffing arbor was one of my better purchases!

I too am a KTM 9 user. I never had an issue such as you are describing. It must have something to do with presure/flow from the gun. I spray fairly heavy coats. (just until it Looks wet). Once in a while I get it to heavy and have to rotate the piece until it sets. If I do get a sag I just leave it and sand it out later.

I Spray during the dryest and warmest weather possible. The only problem I've encountered is not letting it dry well before the next coat. If I don't wait it will cause that dreaded pale blue haze. Under most conditions you can recoat after two - three hours with no problem.

I level sand about two days after spraying then do the finish sanding and buffing about three or more weeks later.

I do spray over epoxy filler that is a continuous coat over the whole thing.

I like the result

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Joe Beaver
Maker of Sawdust

Without actually seeing it, typically yes. Bare wood should have a totally different look and feel. Orange peel happens on all surfaces, even the top.

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Brian

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

https://www.howardguitarsdelaware.com/

Rick, thanks for the link.
Matthew, you're welcome.
I've purchased a buffing arbour in UK to make my own, not as wide but should do when I get it set up.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

no probs Colin, do you mind if I ask where you got your arbour from? ... I've been having a look but can't find anything really suitable.
I see your in Inverurie ... beautiful part of the world, I was at university in Dundee and worked in Perth for 6 years but have been half way round the planet since. I still miss Scotland though.

Joe - yep, I think I was recoating too early as well, at least I got most of my potential balls ups out of the way on my first attempt

Brian, it was all a bit strange, even with the shiny bits I seemed to be back to bare wood around them after sanding, this is what made me unsure of my "is this bare wood or not" judgement. All is since better with my improvement in technique

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imagination is more important than knowledge, knowledge is limited, imagination encircles the world

Yes, I quite like the area, just the weather could be more amenable at times!

http://abcpolishing.co.uk/large-heavy-duty-polishing-spindle/
I emailed an inquiry and they replied
They made one 30" long, 3" threaded each end (LH thread/RH threaded) special order for me with large flanges for 12" wheels
They have a good range of buffing stuff.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

thanks Colin ... sadly with some recent wild expenditure on new bandsaws and spindle sanders divorce would be a definite possibility if I got one of those plus the motor

I'm looking at this instead - or my arms will be called into use and I'll hand buff it :

http://www.amazon.co.uk/Silverline-2645 ... 662&sr=8-3

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imagination is more important than knowledge, knowledge is limited, imagination encircles the world

I've seen some decent finishes done with that type of buffer and by hand.

I know the story......
I bought it because it was cheaper at the time and I had the money (extra of course for the mods)
It's been sitting for some time now waiting on all the other bits, but my last bonus went on a 2nd hand Fuji spray system I saw on ebay and now I should build a spray booth too...... Everything in it's own time.
Like your booth by the way!

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

my booth took a lot of planning and expenditure don't you know - I actually think the overspray finish on the (professional level) cardboard is better than on the guitar .... this is not supposed to be the case apparently lol

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imagination is more important than knowledge, knowledge is limited, imagination encircles the world

Rick, just remembered - this may interest you, when the time comes
http://www.elitetools.ca/en/product/w1681-shop-fox-buffing-assembly/
Says free delivery, but don't think that will apply to international. LOL

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I've sprayed with KTM 9 and EM6000 both. I MUCH prefer the EM6000, although it didn't like thinning with DA, which was required for me to get any decent flow with the KTM9 (didn't thin it a lot, just a teaspoon full for the whole sprayer reservoir. I thinned the EM 6000 with just a little bit of hot water.

I'm not claiming that it wasn't a question of poor technique. That's likely a large part of it, but I just found the EM6000 to be more forgiving, less orange peel, and a very nitro-like finish after buffing. (Still some orange peel, though, just less).