Micro Pitting in CA finish

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Katsin

Katsin

Member
Joined
Feb 26, 2011
Messages
263
Location
Vernon, NJ
I'm getting very small micro-pitting in my CA finish and it is driving me crazy. Has anyone else encountered this?

I've been sanding the blank up to 12k MM, then I clean with denatured alcohol, then about 8 coats of medium CA with accelerator in between each coat. Then I MM up to 12k again and finish with plastic polish.

I was able to reduce pitting by re-sanding the CA a second time but I think I could blow through the CA if I keep at it and end off worse.

Any techniques to try to reduce pitting?

Thanks
 
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Is it happening on all different types of wood? Is your MM pads dirty? If I am working with an open grain wood I do about 4 coats then MM then do 4 of so more. It seems to fill in the voids faster and uses less CA. Any way you could post a picture of the problem?
 
I would use Acetone instead of DNA. All alcohol contains some water and water and CA do not like each other very much. Also I stop sanding my blanks at 600. The CA needs, as does any finish, some tooth to hang onto. You may be getting the wood just too slick for the finish to adhere. Believe it or not, the surface can get so smooth that the finish can not stick to it. Hope this helps.
Charles
 
"pitting" to me says you are too close or putting on too much accelerator. Too close the mist is not fine enough and will put those micro pits in for sure, that is my guess is what is causing.
 
I find that I will get "micro pitting" if I don't adequately smooth the CA surface with the coarsest brown Micro Mesh pad (1500 grit MM = 400 grit ANSI). I always check the surface with 40x magnification and good task lighting prior to moving up to the remainder of the grits. It should be perfectly flat with nothing more than the uniform scratch pattern from the Micro Mesh pad. If any small pits remain, I continue to sand at the coarsest grit until they are completely gone. I am careful, particularly at the ends of the blank not to sand through the CA. You can usually see with magnification, which areas need more sanding. Incidentally, I put on 12 coats of medium CA, using aerosol accelerator after each coat.

Dave
 
hunter-27 said:
"pitting" to me says you are too close or putting on too much accelerator. Too close the mist is not fine enough and will put those micro pits in for sure, that is my guess is what is causing.
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Similar experiences If I overdo the accelerator or I am too close while spraying. I put on two sealing coats of thin CA after sanding only to 400 and then move on to 4 or 5 coats of medium CA with LIGHT accelerator between each coat, spraying from at least a foot and a half away. Sand lightly with 400 to a uniform cloudiness and then start the micro pads. Works for me. Hope your issue is resolved. Combine all the tips and get rid of the DNA and you are bound to find a solution.

Martin

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Here is a picture:

pitting.jpg


I thought the MM to 12k might be overkill before finishing so I will just go up to 600 on my next pen before applying CA. I had actually switched away from acetone to denatured alcohol because all of the fingernail acetone I could find had additives which I worried could be causing trouble. I'm wetting the micro mesh pads and when I examine them closely they don't appear to have much of anything on them that would be causing trouble. Should I expect to scrub the MM with a brush between each use? I only have a spray applicator for the accelerator but it makes a pretty fine mist. I've been holding the spray bottle about 18 inches away and doing 2-3 squirts. I don't think I'm hitting the whole pen from 18 inches unless I do at least 2 squirts.

Thanks for the input!
 
Kastin, Monty, a member here, has some refillable airisol cans that work very well for spraying accelerator. He also sells bulk accelerator and the best CA I have found. Stay away from the fingernail polish acetone. It has oils included that may cause other problems. Your local BORG or WalMart will have it in their paint department. That will be clean acetone. Be very careful with it as it is flammable and will take the oils from your skin if you do not protect your hands with good gloves. Monty's website is;
http://woodenwonderstx.com/WWBlue/index.html. Give him a check out. If you do not see what you need displayed, just send him a question. He is very helpful. Normal disclaimer, I have no connection with Monty except to make purchases from time to time.
Charles
 
Looks to me you are not sanding with 400-600 long enough to get the little pits sanding out. By the pic I cant tell though if the white spots are under the CA or not. If they are not that is CA dust in the holes
When you sand with 400 after you get the high spots down whipe with you finger across the blank The dust will fill the holes in and you can see how much more you need to sand. Dont wipe of with any liquids because that will wash out the holes. After the little holes are gone go to the micr mesh wet with a little dish soap in the water.
After you do enough pens you will know just how much sanding it takes so you dont go through.
Also if the pits are too deep clean the blank really good with mineral spirits. to get all the dust off and out of the holes then apply a few more coats of CA to fill them in.
Now if the white dust spots are under the CA sand back down to the wood and start all over.
This is what i do but like everyone says There are hundreds or more different ways to do it.

Also A little bit of accellorator goes a long way. and causes white spots if it is not a fine mist.
 
Thanks everyone for the great feedback. So much to think about and try.

I am using Monty's CA and accelerator but he I think he was either out of the airisol cans or they felt over my budget at the time I ordered. Given what everyone has said about the distance and fine application helping I may rethink that.
 
I will agree that the MM before applying CA is not needed at all. I would sand to about 800 grit. I would stop the lathe and sand with the grain. Then wipe down with whatever you want. Most people will use the accelorator as the wipe down substance. The key here is to make sure it is dry and by turning the lathe back on and let the blank spin for a minute or two. If this is wood with deep grain patterns or voids then use about 3 coats of CA. Sand down again with 800 grit paper and repeat first steps. You should now have the voids filled and ready for you normal CA steps and then MM. I avoid using Accelorator but most off avoid the spray bottles. The aireosals cans are better if needed. I would never use 10 coats of Medium CA either. too much of a build up unless you planned when you turned the final dimensions on the blank.
 
Would it matter if I were using regular versus mild accelerator? I was using regular accelerator. I have no idea how much of a difference regular versus mild would make.
 
I think the vast majority use regular accelerator. I would suggest that if you wipe the blank with anything after sanding, use accelerator in place of acetone or DNA.
 
You are advancing too quickly through the micro mesh stages. makes sure that you have a completely smooth surface before advancing to the second pad. I find that dry sanding with 400 grit sandpaper helps me see the pitting better (the low spots remain shiny). Once all the low spots are gone, I switch to wet sanding with the micromesh and progress carefully through each grit.
 
spnemo said:
You are advancing too quickly through the micro mesh stages. makes sure that you have a completely smooth surface before advancing to the second pad. I find that dry sanding with 400 grit sandpaper helps me see the pitting better (the low spots remain shiny). Once all the low spots are gone, I switch to wet sanding with the micromesh and progress carefully through each grit.
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Agreed.

If there are any shiny, low spots... do not proceed, or you will end up with imperfections in your finish. Either keep sanding with 400 grit until they are gone, or apply a few more light coats of thin CA. Then go back to the 400.

Once you get a uniform, dull, smooth surface with the 400 grit, continue to higher grits and there should be no more pits in your final finish.
 
I definitely haven't developed a good sense of how long to work each grit on the MM pads yet. I think I've been spoiled by the full acrylics where it is so easy to sand and see the result.

I'm thinking a loupe or magnifying glass may be helpful while I get a handle on it.
 
A magnifying glass is helpful but good lighting placed at the propper angle to the blank will make the pitting show up really well. I have a 60 watt incandescent daylight bulb behind my lathe - about 8" behind, 6" up from the centers, and a few inches to the right of the tailstock center. The bulb is pointed toward the blank. This way every little pit shows up as a shiny spot. When I am sanding with 400 grit, I can often tell when I am getting close by looking at how much the blank shines as it is spinning. More shine means more pitting.
 
Try to spotlight the work. Check. My work table fluorescent doesn't light it as well as it could.

I'm hoping to try another wood pen this upcoming weekend and apply some of these suggestions.
 
I used to experience this and can duplicate the pitting by applying medium CA too thick and too fast. And it is usually compounded by some accelerators. I have done that on pens in the past, and on duck calls and also on tumblers. I usually just clean the spots and either add several levels of thin CA on top or sand down to get those little pits out.

By the way, you can't make it too slick for CA to adhere. CA can and does stick to auto glass. I have seen houses painted around the windows with drops of paint on the window that takes razor blade scrapers to get it off. CA sticks much more so than paint. IF there is something under it to prevent it from sticking, that that can happen - as in oily blanks, but that is not the problem here. I have finished sanding numerous pens with 12000 MM only to find the blank end being .006 - .008 too small. So I added a few layers of thin CA directly on top of that to build it up and then re-sand. I never had a problem with those.
 
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I did another pen and it was a complete wrestling match but to the unaided eye the finish appears pretty much dead on. You can see a lot of fine scratching in this closeup but there is really no pitting.

pen12closeup.jpg


I am very happy with the way the finish on this one turned out though I am not sure I could re-produce it since it was such a battle. I did take into account a number of your suggestions including wiping the blank down with accelerator to clean, spraying less accelerator, sanding only to 600 before CA finish, examining the sanding more closely under light.

Thank you everyone for your suggestions!
 
Katsin,

Don't worry about the "battle" because in truth, it is the battles that you gain your greatest experiences. And it is these that also make you into a good teacher for others. I don't like them either but I learn something from them each time.

I haven't made a pen in over a year because of work and a move from Japan to the US (and my lathe is still apart and in a box) but I still remember the battles. I know to expect a battle when I need to get a few good pens out when it is cold and my shop only heats to about 50° to 55°F. The battle doesn't always come but when it does, I know from experience that it may take a 3rd or 4th or 5th turning, sanding, re-CA, sand, re-CA etc.

I don't go for the heavy production but more for 2 or 3 at a time for friends of gifts that are all one of a kind.

Your pen looks great! As to the scratches, do you use 12000MM? Also, I used to be able to produce photos that cause scratches to appear on a pen that didn't have them - strictly from the lighting and camera angle. Fluorescent light and diffuse lens plus camera angle will do this.
 
I do use micro mesh up to 12k on the finish.

You mention a cold shop. I've been working in my garage which is only about 40 degrees lately. There will be more humidity in the summer but perhaps the heat will help.

Photo setup is awful. I only have a snapshot camera and no special lighting. Photos got a lot better once I started using a tripod and the timer to avoid camera shake.
 
My pens almost always end up with fine scratches like that, even after Micromeshing.

Buffing will eliminate those scratches. I used to just use White Diamond, which worked well enough, but recently switched to 2 plastic polishing compounds from caswell plating.

- Joe
 
Katsin said:
You mention a cold shop. I've been working in my garage which is only about 40 degrees lately. There will be more humidity in the summer but perhaps the heat will help.
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Ahh, That is what I would say is a major contributor to the problems of both the pits and the battle. For me and from my own experience, CA works best above 60°F. I don't use BLO that much but BLO does help me some in lower temps - 50°F and above. I just don't do pens below that. The battles become too great for me.

Also, as Joe mentioned above, I use rubbing and polishing compounds often too.
 
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I haven't had a chance to read these other posts, so this may be redundant, but in my experience that's caused by two things: 1) an insufficeintly smoothed pen barrel, and 2) using the accelerator, which causes rapid and therefore uneven curing of the CA. My solution has been to use a blow dryer to keep the barrel warm (and dry) which evenly cures the CA (Berea's Triple Distilled Thin, in my case) and obviates the accelerator.
 
Kokopelli2010 said:
Are you using compressed air with a cloth to "blast"off any residual sanding dust off pen before moving to next grit?
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No. When cleaning the blank I've only been wiping down with accelerator (before CA) or dry cotton (after fresh CA applied).

I'll have to move the compressor buy the workbench to add it to the cleaning options. Thanks.
 
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