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G.Cummins
PostPosted: Tue Sep 09, 2014 12:58 pm 
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Hi All.

Hope some-one may is able to shed some light onto my latest finishing problem.

I have finished buffing my latest project which I finished with Melamine lacquer. I Noticed after final buffing I still had some small scratches in the upper shoulder which I missed. I went back to the buffer and started this time with glosswax 16 (olive colour) on a G weight 12" buff (second stage of my polishing schedule), after one pass I stopped to see what was what and now there are lots of tiny uniform blemishes in the finish as it something was on the buff and has dug into the finish and dragged slightly (imagine a pin prick with a tail). Size is about 1mm. I have checked the buff for contaminates and nothing is obvious, could the dry compound have caused it? Any-one else have this problem? I have noticed when buffing in the past these blemishes are sometimes left over but they have always rubbed off with a paper towel.

I am using a homemade buffer which spins at approximately 1000 rpm.

I am stumped and frustrated.

As always it is impossible to photograph such small things with a glossy background.

Any help is gratefully received.

Thanks
Glenn.
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RusRob
PostPosted: Tue Sep 09, 2014 1:22 pm 
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Have you used a spur on your wheel? If not then it probably has something stuck in it. Sometimes you can get a spot of built up or even something stuck in the buff, in it which can easily show up as what you are explaining. If you don't have a buffing spur then you can use a flathead screwdriver that you don't care about but a spur will work much better because it can get deeper into the buff.

It is also important to get all the old compound out of your wheel before using it since dried compound will only scratch the finish. A clean buff will always give you a much better shine than a dirty one.

Bob
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Glen H
PostPosted: Tue Sep 09, 2014 7:19 pm 
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Have you tried to rub them off with a little but of naphtha?


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bluescreek
PostPosted: Wed Sep 10, 2014 5:52 am 
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You are using the wrong compound. I use Mazzerna 16 and 18 then to get rid of the tinniest swirl marks I use 3m finnese it and Maqures swirl remover #9
also I use a soft flannel wheel , What wheels you using? I am also turning about 750 RPM.

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B. Howard
PostPosted: Wed Sep 10, 2014 7:43 am 
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First thing I notice is that 1000 rpm is a bit fast for buffing lacquer, That's about 3150 fpm surface speed. Ideally you want it a bit slower, around 2700 fpm.

Second, were these sanding scratches from the level sanding or buffing scratches from the first buff? If they were sanding scratches the compound you chose was to fine to remove them. If this was the case you likely used extra pressure to try and remove them and started to burn the lacquer a bit. You should have either went back to the first compound or used a finer grit paper to remove the scratches before buffing with the GW16.

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lespaul123
PostPosted: Wed Sep 10, 2014 8:09 am 
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Now I am not sure because I use a different system than you, but I think you may have overheated the finish. I recently did this myself. After I lifted the pad to look at the finish, it looked like it had a bunch of tiny raised pock marks. I had to strip and refinish the area to fix the flaw. Can you feel the blemishes? Are they raised?
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G.Cummins
PostPosted: Wed Sep 10, 2014 12:40 pm 
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Thanks for the reply chaps.

Lespaul123 - No not like pock marks and doesn't feel raised. It looks more like if you could imagine, putting a fork in mashed potato and dragging it through(on a smaller scale if that makes sense). I didn't use much pressure when holding the guitar to the mop.

Brian / John - The scratches were left from the level sanding with p1200 grit wet & dry, I think I must have missed that section on the first buffing stage. The first compound I used was Menzerna Glosswax 18 on a B quality 1.5 x 12" mop, Then Glosswax 16 on a G quality Mop, then Atol 6 on a G Mop. http://www.thepolishingshop.co.uk/acata ... _Mops.html. I will go back to my 2" pulley from a 3" on the drive that should slow her down abit.

Should the compound take care of the scratches quickly? I noticed it took a bit of time for them to disappear. I put that down to only using a 1.5 inch mop. First stage buffing took roughly half an hour to get rid of the scratches on the top.

Glen - I have, unfortunately no joy.

Bob - I did use a mop dresser but don't think I got rid of all the previous compound. Looking at the mop now it does reveal a build up of compound only on one section of it the rest looks clean. That could have been the cause. Does that spear do a good job getting rid of the dried compound? I'm having a look at it now, looks pretty well stuck on.

Again thanks for taking the time to reply.

Glenn
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bluescreek
PostPosted: Wed Sep 10, 2014 7:05 pm 
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the one thing here is what buffing wheel are you using. As Brian points out , you look at Ft/p/S. I have a 12 and 16 in wheel on my buffer. I also use soft cotton and flannel buffs. I also use a rake , over time some compounds can harden and your buffer can become a grinder.
Pressure , rate of feed and how much material you load all come into play.

I will usually wet sand to 1500 grit , depending of the flow I use 800 - 1200- then the 1500. Sometimes I can use a dry 800 but wet sanding will make your sandpaper last longer. If your finish isn't cures you will load the paper no matter what.

Once I am level I start with the Mezerna , I use a naphtha wipe if water won't clear the paste , that sometimes will form. I also want to see a light dust form in front of the wheel. I also have my hand low so I can feel if there is a heat build up.
Once I am done with the Mazzerna , I go to 3M finnese it, This I just rub on the body and buff after raking the 16 in wheel. This will get a higher degree of shine , and the I finish off with Maquires swirl remover , and lastly I hand rub with Imperial hand glaze.

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Glen H
PostPosted: Wed Sep 10, 2014 8:39 pm 
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John, are you saying that you use a wet polish on a buffer wheel? Curious because I didn't know this would work well.


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guitarguitar
PostPosted: Wed Sep 10, 2014 8:46 pm 
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You may have some (trash) ie contaminants in the finish that you are sanding/ buffing into and exposing. I call them comets because that always seem to have a tail depending on the buffing angle. If you suspect this may be true, two choices. Keep buffing and hope you pull them out before you burn through the clearcoats or reapply clear over the affected area. Welcome to finish hell.

Skip
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RusRob
PostPosted: Wed Sep 10, 2014 8:54 pm 
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Glenn,
I don't have a lot of experience using a fixed buffing wheel but I do have thousands of hours buffing cars. I worked as a auto painter for over 20 years and mainly used lacquer so lots of wet sanding and buffing with a hand wheel.

I could be wrong but what you are describing sounds to me like there is something in your buff that you need to clean out. A buffing spur will remove almost everything it the buff as long as it is not something like glue or physically hooked into the fibers. From your last comment it is my guess that you have some compound buildup that is now collecting lacquer bits as it spins. Since you are running a little bit fast you very well could be melting the lacquer and it is collecting in that spot. A spur will clean it out.

Below is a picture of what I am talking about. You see it looks just like a spur that you use for horses... hence the name spur... As you push it into the buff the little prongs spin and will pull out any crud in the wheel.

I personally do not use a buffer on guitars and prefer to hand buff all of my finishes. I prefer to go slow and inspect my work very closely so hand buffing affords me that. I also enjoy the quality time I get. I guess that is why I prefer a French Polishing.


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RusRob
PostPosted: Wed Sep 10, 2014 9:00 pm 
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guitarguitar wrote:
You may have some (trash) ie contaminants in the finish that you are sanding/ buffing into and exposing. I call them comets because that always seem to have a tail depending on the buffing angle. If you suspect this may be true, two choices. Keep buffing and hope you pull them out before you burn through the clearcoats or reapply clear over the affected area. Welcome to finish hell.

Skip


That could also be the issue... You can easily tell if the spots stay in the same place and do not appear in other places where you have buffed. If that is the case then just hand buffing those spots should take care of it. Unless they are really noticeable you should not have to re-spray... That would be used for a last resort effort to me.

Bob
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bluescreek
PostPosted: Wed Sep 10, 2014 9:13 pm 
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yes I use a wet polish
I put that on the guitar and use the fresh raked wheel to buff

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Glen H
PostPosted: Wed Sep 10, 2014 9:41 pm 
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Thanks John. I may have to give that a try.


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G.Cummins
PostPosted: Thu Sep 11, 2014 10:05 am 
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I had up until recently rubbed my finishes out by hand but the lure of the buffing wheel in thinking it would make things easier was to strong.

guitarguitar wrote:
Welcome to finish hell
Haha, What with difficulty finding suitable finishes in the U.K then trying to make them look like a mirror, it is indeed.

I think you are right Bob. Seems like it could be something on the wheel as it left the marks every where I touched. I'll grab myself one of those spurs.

Buffing with wet compound does sound interesting.

Cheers.

Glenn.
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Wes Paul
PostPosted: Thu Sep 11, 2014 10:42 am 
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Im having trouble removing all the scratches in my finishes. I have been sanding to 1500, buffing with the pre polish, then intensive polish, then meguiars swirl remover by hand. Am I missing a step?


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Barry Daniels
PostPosted: Thu Sep 11, 2014 3:20 pm 
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I gave up on Menzerna and have switched to wet automotive compounds and foam pads. The auto guys have been improving their products a lot in recent years whereas the Menzerna is a bit old school, IMO.
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G.Cummins
PostPosted: Fri Sep 12, 2014 9:33 am 
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Wes,

I am finishing off with Atol 6 but if your scratches look like sanding scratches you may be doing what I have done and missed them in your initial buffing.

I have found it takes a long time in removing p1200 sanding scratches with the pre-polish and had to repeatedly go over the same areas a number of times and I still missed a section.

Bad news in my case as I went back to remove the marks left in the finish and have sanded through. Not afraid to say I nearly wept.
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RusRob
PostPosted: Fri Sep 12, 2014 10:14 am 
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Wes, Again I have no experience using stick compounds or a stationary buffer but I do know a lot about buffing lacquer with a hand buffer and by hand.

It almost sounds like you are not using a coarse enough compound as your first stage. Think of buffing just as you would sanding. You start with coarse grits and end with fine. What you want to do is if you finish sanding with 1500 grit you probably want to start buffing with a coarse grit and move to finer and finer as you progress. My final sanding is with 2000 grit paper and I use 3 different compounds plus a good swirl mark remover.

What may be also happening is you are allowing your sandpaper to load up with gunk and it is producing scratches.

It also could be is that you are not sanding the coarser scratches out before moving on to finer grits.

A trick you can use is to place a light source behind the area you are working on and look very closely at the surface of your finish as you work (the light will be facing you on the other side of the guitar) . Some people do not quite understand how to look at a surface they are sanding and tend to look at the reflections instead of the surface. It is a bit tricky to explain but it is all about your focus point. When looking at the reflections they are actually focusing at a greater distance than the surface where the scratches are.

But it sounds like you are skipping a step somewhere and moving on to finer grits before you get the heavier scratches out.

That is one of the reasons I like to do all of my buffing by hand. It gives me time to look closely at every spot I sand or buff.

Hope this helps.

Bob
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RusRob
PostPosted: Fri Sep 12, 2014 10:20 am 
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G.Cummins wrote:
Bad news in my case as I went back to remove the marks left in the finish and have sanded through. Not afraid to say I nearly wept.


That shouldn't be too big of an issue if you are using lacquer. I don't know what spray gun you are using but you should be able to adjust it to a very small fan pattern and spot finish them. Just mix your finish a little thinner and spray more coats starting small and working out from the spots. They should buff out just fine as long as you blend the edges out. I have done it many times and it isn't too big of a deal (just part of the game...)

Cheers,
Bob
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G.Cummins
PostPosted: Fri Sep 12, 2014 12:11 pm 
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I originally applied the Lacquer by brush. I'll be using a rattle can for the repair (same product but in aerosol).

I was considering re-finishing the entire top, the concern being that if I only do one section it would show as a raised area. I'll try the spot fix and see how it goes.

Cheers.
Glenn.
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RusRob
PostPosted: Fri Sep 12, 2014 1:24 pm 
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Aarggg... spray bombs can be tricky to do spot repairs because the dont atomize the material to give you a smooth edge to keep from getting witness lines around the edges. But you my give this trick a go... take a piece of heavy cardstock big enough to cover the width of the spray pattern of your spray bomb and cut a hole in the middle of it the size of the spot you want to spay. Then hold it a few inches above the guitar and spray the cardstock. This will act as a loose mask so you can be more precise where you are applying the clear. By moving the cardstock you can feather the edges a lot easier and with more controle than just using the spray bomb.

Just dont get the cardstok too close to the guitar or it will leave a thick edge or worse touch the wet lacquer .....

Bob
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Wes Paul
PostPosted: Fri Sep 12, 2014 4:47 pm 
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RusRob wrote:
Wes, Again I have no experience using stick compounds or a stationary buffer but I do know a lot about buffing lacquer with a hand buffer and by hand.

It almost sounds like you are not using a coarse enough compound as your first stage. Think of buffing just as you would sanding. You start with coarse grits and end with fine. What you want to do is if you finish sanding with 1500 grit you probably want to start buffing with a coarse grit and move to finer and finer as you progress. My final sanding is with 2000 grit paper and I use 3 different compounds plus a good swirl mark remover.

What may be also happening is you are allowing your sandpaper to load up with gunk and it is producing scratches.

It also could be is that you are not sanding the coarser scratches out before moving on to finer grits.

A trick you can use is to place a light source behind the area you are working on and look very closely at the surface of your finish as you work (the light will be facing you on the other side of the guitar) . Some people do not quite understand how to look at a surface they are sanding and tend to look at the reflections instead of the surface. It is a bit tricky to explain but it is all about your focus point. When looking at the reflections they are actually focusing at a greater distance than the surface where the scratches are.

But it sounds like you are skipping a step somewhere and moving on to finer grits before you get the heavier scratches out.

That is one of the reasons I like to do all of my buffing by hand. It gives me time to look closely at every spot I sand or buff.



Thanks Rus!!! Those are definitely helpful tips. I will go for a new coarser stage buffing after sanding. I do need more light In my shop when finishing the light behind it is a great tip!
Only recently on my last few guitars I have gotten more comfortable spraying the lacquer without turning it into the next thing I have to learn to fix.


Also I have a hard time finding a good source for wet/dry sand paper. Even at the paint supply stores I go to they will have the grades mixed up and mix matched brands. Its hard to tell in the higher grits weather its finer or not.
Can you recommend a good affordable source for sand paper?




Hope this helps.

Bob
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Wes Paul
PostPosted: Fri Sep 12, 2014 4:50 pm 
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Sorry bout that last post there all mixed together!!! haahahha

G.Cummins:

Thanks for the tips too!!!! Sucks sanding thru I feel your pain!!
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RusRob
PostPosted: Fri Sep 12, 2014 5:17 pm 
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Wes,

Sandpaper can vary from manufacture to manufacture as far as quality goes. I almost always buy 3M because their quality is always consistent and I know what I am getting every time. I wouldn't skimp on trying to find cheap paper because that is just what you get. Cheaper papers will end up being inconsistent as far as grit as well as the adhesive that holds in on. When that fails you will end up with grit all over your finish and it will lead to scratching the finish rather than sanding it. A good quality paper will also last much longer which will actually save you money in the long run. I keep my paper clean by having a spray bottle with a couple drops of dishwashing soap in it. The soap lubricates the finish which keeps the buildup in your paper down. I keep a small piece of plastic handy (like a cut up credit card) so when my paper starts to build up I wet it down and scrape the buildup off. That will make you paper last much longer and will keep it from scratching the finish. You can feel as soon as the paper starts to build up because it stops cutting. If you keep it clean, a lot of times you can save it and reuse it on another job as long as it is still cutting.

You can usually find 3M sandpaper in a lot of auto body supply stores. You can also find 3M rubbing compounds there as well. Most good body and paint guys demand high quality materials so suppliers usually carry 3M products. Yes they are more expensive but worth it and once you start using high quality materials you will understand that it is really cheaper in the long run.

Cheers,
Bob

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