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Having difficulties with polishing
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=17987		 Page 1 of 1
Author:  Neil Gardiner [ Mon Jul 14, 2008 10:08 am ]
Post subject:  Having difficulties with polishing
Hi all

Working on my first guitar. Finished the body with KTM-9 and the neck with varnish.

I let them cure for about 3 weeks. Then wet sanded to 1200.

Then I tried to polish them. I have liquid polish compound from Lmi - cut polish, fine and extra fine. I got foam buffing pads from Stew Mac that go into a hand drill.

So, when I tried to polish I applied the polish with a cotton rag and removed the excess. Then let it dry. And then used the buffing pads. I have only managed to get a very low gloss finish. And on the Varnish it came out quite blotchy.

Am I doing something wrong? Is there another method you might suggest?

Thanks
Neil
Author:  Steve Saville [ Mon Jul 14, 2008 10:25 am ]
Post subject:  Re: Having difficulties with polishing
You need to wet sand to at least 2000. I go to 4000 before polishing.
Author:  Hesh [ Mon Jul 14, 2008 11:24 am ]
Post subject:  Re: Having difficulties with polishing
Neil buddy even though I never used the KTM9 that I had the curing for 3 weeks caught my attention.

With nitro there is a huge and noticeable difference between letting it cure 2 weeks and 4 weeks. I am wondering if the finish was not completely cured at 3 weeks.
Author:  Cecil [ Mon Jul 14, 2008 11:37 am ]
Post subject:  Re: Having difficulties with polishing
Neil,

I have used KTM9 but never the compounds you mentioned.
Steve has it right. Wet sand to at least 2000. you can polish from there but it will take a little more elbow grease.

I polish by hand with 3M finess It, Perfect It, and finish with Show Car Hand Glaze. I never got a really clear finish until I found the Hand Glaze. You can get these products at your local auotomotive paint store.

I can't help with the varnish.

Cecil
Author:  Barry Daniels [ Mon Jul 14, 2008 11:57 am ]
Post subject:  Re: Having difficulties with polishing
neogardguitar wrote:
So, when I tried to polish I applied the polish with a cotton rag and removed the excess. Then let it dry. And then used the buffing pads.


That does not sound right. Apply the polish and then use the buffing pads. You do not want to remove the polish and let dry. The polish has to be on the surface and wet in order to work with the buffing pads.
Author:  Michael Dale Payne [ Mon Jul 14, 2008 4:47 pm ]
Post subject:  Re: Having difficulties with polishing
KTM9 will completely cure in 7-10 days at 80 deg F and 40% rh. in 3-5 days at 90%

I suggest you sand through at least 2000p or 3000p or even better 12000 micromesh.

Also if using a battery powerd hand drill you not likely to get a very high rpm and hp out of the drill. a good 3/8 high hp cord type hand drill can get the job done but nothing beats menzerna med fine/ fine / extra fine compound on a high speed buffing wheels. I never had good luck with a hand held.
Author:  Jeffrey L. Suits [ Mon Jul 14, 2008 9:50 pm ]
Post subject:  Re: Having difficulties with polishing
neogardguitar wrote:
Hi all

Working on my first guitar. Finished the body with KTM-9 and the neck with varnish.

I let them cure for about 3 weeks. Then wet sanded to 1200.

Then I tried to polish them. I have liquid polish compound from Lmi - cut polish, fine and extra fine. I got foam buffing pads from Stew Mac that go into a hand drill.

So, when I tried to polish I applied the polish with a cotton rag and removed the excess. Then let it dry. And then used the buffing pads. I have only managed to get a very low gloss finish. And on the Varnish it came out quite blotchy.

Am I doing something wrong? Is there another method you might suggest?

Thanks
Neil


Those polishes are not meant to dry on the surface. I concur with others who feel 1200 is not
fine enough sanding.

If you haven't used Buflex abrasives, you're in for a treat. LMI carries them now. Just miraculous...
Look them up at Eagle Abrasives.
Author:  TonyFrancis [ Tue Jul 15, 2008 3:56 am ]
Post subject:  Re: Having difficulties with polishing
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Author:  Richard Wilson [ Tue Jul 15, 2008 6:43 am ]
Post subject:  Re: Having difficulties with polishing
Yeah I'm a bit confused as well with all this 2,000-12,000 sanding. I do normal nitro finishes, and typically only sand to 800 then go medium/fine/very fine with the polishing that is enough to get very nice gloss finishes. Is there something fundamentally different about waterbase finishes that requires such fine sanding?
Author:  David R White [ Tue Jul 15, 2008 5:48 pm ]
Post subject:  Re: Having difficulties with polishing
The level of sanding should depend on the polishing compounds you are using. I use the Menzerna pastes and they specifically say to sand to 800, which is what I do and it works fine. While I don't disagree with Michael about a high speed buffer being better it is certainly possible to get a high gloss with a low speed device (I use a ROS).

I agree with Barry, that the problem is the application method, that it should be applied and "buffed" with the drill while still wet.
Author:  JRE Productions [ Wed Jul 16, 2008 4:03 pm ]
Post subject:  Re: Having difficulties with polishing
I do a lot of refins with Lacquer. I let cure for 30 days (for a total refin) before the next stages. I have not worked with the product being disucuss and it sounds like it cures faster. Unless the rubbing compound is pretty course (which is could be), I usually go to at least 2000 grit and often 2500 in 200-300 incriments starting around 800. I then use a fine rubbing compound and then a glaze that gets the final stroke marks out. I do all by hand, no power tools.

Here is one I did last year. 1973 Les Paul Goldtop.

Image
Image

Its hard to see in this light, but if you look at the heel, cutaway and others where the light is more direct, you can see how deep the finish is.

Here is a 57 Gretsch. In the picture it had been sprayed a few hours earliers. So you can see the finish is quite glossy before any sanding too:

Image
Author:  JRE Productions [ Wed Jul 16, 2008 4:07 pm ]
Post subject:  Re: Having difficulties with polishing
One trick (and a often mistake when not done) is to use a sanding block for all wet sanding. Part of the "glass" like finish is caused from the finish being completely flat. You may start with an orange peel and end up with a swiming pool if done by just fingers. I prefer to use a small gum style eraser as my sanding block. Even the old "pink pearl" works great. It is flat yet soft. Wrap the paper around it and sand in small areas. Keep the paper moist with water or baby oil. Change water/oil as you change grits. If you can keep the finish very flat, it will shine like an SOB!

Joe
Author:  Howard Klepper [ Thu Jul 17, 2008 9:46 pm ]
Post subject:  Re: Having difficulties with polishing
First off, grits must be specified as P system or CAMI. Big difference. The N. American manufacturers used to be CAMI and the Europeans P system. Now a lot of the N. American papers are P, too.

Next, you have some choices as to how far you go on paper grits, and when you go over to compounds--they overlap. It's partly personal preference, party what power sanding or buffing systems you have, partly what particular papers and compounds you are using. Experiment and find a system that works for you.
Author:  SniderMike [ Thu Jul 17, 2008 10:37 pm ]
Post subject:  Re: Having difficulties with polishing
Howard is right on the money. There is a huge difference between 1200 and P1200. P1200 is more like 600 or 700 CAMI.
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