CA finish - small scratches

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george

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Jan 17, 2006
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Ljubljana, Slovenia.
Hy !

I have a problem with CA finish, for which I would really appretiate any advice. I use CA glue as a sanding sealer, and work on bare wood up to 12000 MM. Than I do 3 layers of thin CA (tryed with paper towel, small pads ), without saning in between. Than I leave final coat to dry ( last time round 4 hours), and than light saning with 600 ( or 800), and than up to 12000 MM.

But at this final sanding with 600 I get small scratches ito the CA coat. That is also the reason that I dont do sanding betwenn each CA layer. I always do "horizontal" sanding for removing sanding lines, but at this level this does not help.

I think I make scratches into the the CA layer - I have CRAFT SUPPLIES ca brand. Do you think that this CA is to soft ? But the protection of the wood is very well.

I have read many CA advices on this site, I work by Russ Fairfeild DVD's instructions, but can not resolve this problem. Thank you for help in advance, have a great new year. George
 
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George, Sounds like your problem is mainly due to sanding.
Do you clean off the blank between each grade of sanding medium with soft cloth? If you don"t this means that particles of that sanding grade could be left on thw blank and picked up by the next one. This can cause scrathcing that you haven't even thought about. These might not be apparent until you apply the finish.
Do you really let you CA dry? I know you say so but weather can effect this.
I would seriously look at using wet/dry paper or cloth and wet sand. you will find a comparison chart somewhere in these forums regarding the fineness of various grit sizes vs MM
 
I do three layers of medium to thick CA after a couple of sanding sealers. Bare in mind that Russ has his down to a science - for him. The amount of pressure he uses in applying CA may be different from yours; the amount of sanding pressure might be different too. I occasionally get a few scratches too. I sand them out and if I feel I have come close to sanding all of the surface CA out, I add another medium coat or two.

I recently did a couple of duck calls and the Rosewood had a fine scratch deep inside the CA on the mouth end. I had to sand it down to get it out and then build a coat back up. These are the 8th and 9th calls that I have made, so even with experience, a scratch or two will occasionally rear its head that successive finer sandings don't get out.


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The inconsistency caused by changing brands, different brands or cheaper brands of sand paper will cause scratches more than quality or staying with one brand does. If one brand does cause problems consistently, change brands to a better brand. There is a brand here that I get more scratches with at 600 than I do with another brand at 400.

BY the way, as I read your post, I see two separate problems that are kinda mixed in as one. 1. Coats of CA probably too thin; 2. Sandpaper grade inconsistent, but that could be a technique problem.
 
Hello !

You guys really work fast. I thanks all for comments. I will try with thicker coats of CA and longer drying time. I have normal wood sanding paper up to 400 grit, 600-800-1000 are from car industry for fine polishing ( I dont get wood sanding paper of this grits in my country). I will try also just MM after CA coats.

I think that CA finishes are quite easy to learn up to 80 % of the process. But that 20 % for GREAT look take paitente and time.

Thanks again to any future comments, George
 
Originally posted by george

Hello !

You guys really work fast. I thanks all for comments. I will try with thicker coats of CA and longer drying time. I have normal wood sanding paper up to 400 grit, 600-800-1000 are from car industry for fine polishing ( I dont get wood sanding paper of this grits in my country). I will try also just MM after CA coats.

I think that CA finishes are quite easy to learn up to 80 % of the process. But that 20 % for GREAT look take paitente and time.

Thanks again to any future comments, George
Click to expand...

I couldn't have said it any better.
 
The scratches are from sanding. They could be in your sanding sealer coat before you even start applying your finish. As said, make sure you use good quality sandpaper, clean the blanks between grits, and sand both directions with each grit eliminating the scratches from the previous direction. If there is still scratches when you're done sanding, you missed them on an earlier grit. It's hard to tell for sure at the coarser grits and sometimes you might have to go back to the coarser grits again. Maybe try more light at your lathe at different angles to make sure there there is none. If your CA is going on the blank somewhat smooth, I don't see a reason to sand between coats.

Something that hasn't been said yet is buffing. Depending on how deep these scratches are you can try a buffing compound or scratch remover. Lots of people use them to do a final polish.

One more thing that I personally think helps is after the final coat is pretty much set up, I give it a shot of accelerator and it seems to make the CA cure harder. It could be my imagination but it seems that way to me.
 
When I finish with the CA coats I wet sand with MM and then buff. I don't use regular sand paper on CA unless I am trying to remove it.
 
Your problem is probably with the quality of the sandpaper. Cheap is not always best, and cheap means there is a greater possibility of having a few stray larger particles on the surface. If you aren't using 3-M or Norton sandpaper, you should. The Gatorgrit that Ace Hardware sells is also a good quality. Everything else can be a risk.

Some people use Micro-Mesh for all sanding because of the quality and uniformity of the grit particles. That quality comes at a higher price.

Another thing. Are you sure these scratches on the surface of the CA, and not being telegraphed up from the wood. There is a good possibility that those scratches are there on the wood surface from the coarsest sandpaper you used on the wood, and they weren't visible until the higher gloss CA surface was there to magnify them.

You can do several things to reduce the scratches on the CA surface.

- Drag the surface of the paper over the edge of a piece of steel a couple times. This will break off any high spots and leave the grit on the surface more uniform in size. This works for all sandpapers, even 600-grit.

- Wet sand with wax as a lubricant. This reduces the depth the grit will cut and there is less chance of scratching.

- Always sand in both directions - around the piece with the lathe running, and along the length with the lathe off. This is just as important at the finer grits as it is with the coarser.

- Keep the sandpaper moving when sanding with the lathe running.

- And, always use a light touch. Just hold the sanding medium to the surface and let it cut by itself. Higher pressure on the sandpaper doesn't make it cut faster.
 
Hello, me again.

Im getting qiute frustrating with my CA finish. I have tryed almost everything suggested, I have tried at least 20 times on different ways, but I still end up with small spiral sctraches in CA finish.
The surface shine and touch are great, I have nice polished wood without any marks before applying CA, it is also good after 4 layers of CA, but than it starts. As soon as I try to lightly sand with 800 or 1000 or even 4000 MM, i damage the CA layer.

It gets spiral marks inside the CA and I can not get them of - of
course it goes with a lot of sanding but than I end up with CA being sanded of the wood, and Im on the start again. This schratces are not seen at all angles, but they are there if you look at right angle. And they are disturbing.

I was jut thinking - I damage the CA layer with final sanding. I use very light touch, but dou you think that presure on the CA would be smaller with final wet sanding ? I would very appretiate for this comment and any instruction of how to wet sand with 800 or 1000 paper and MM ( what is used for "wetting" )?

I have tried with THIN and THICK CA, without and without accelator ( I have waited for 1 and 2 minutes after final CA), and belive that thin CA is less damaged. I wait before applying next CA layer, I use light touch, and to avoid possiblity of bad quality sand paper I have tried with just 4000 MM after the CA has been dry. But than the surface was quite unpleasent for touch.

I have read almost all help on this forum, but why am I the only with this stupid problem ? Otherwise I like this CA so much, I would really like to master it.

Thanks all in advance for help. Thanks also or past advices. George
 
George: "This schratces are not seen at all angles, but they are there if you look at right angle. And they are disturbing."

First of all I want to say that if you are going to this extent to notice the scratches, you are going to have some beautiful finishes down the road. It says that you care enough about the finish to look at it from all angles. This is good and will benefit you if you just keep at it and don't let the frustration at the moment stop you.

I don't know what the problem is for you but I can only list the things already listed above. If you are not using poor sandpaper, it could be irregular pressure and the amount of time (seconds) you spend sanding with different grits.

One thing that I do sometimes after I get a smooth surface is that I use a very mild automotive rubbing compound for a few seconds turning at 600-800 followed by micro-compound (.2 mu) and then paint/finish polish. Sometimes I just try this as well as other methods just to be trying something different and then compare it to the standard method of MM through 12000.

IF the scratches are not deep, buffing may get them out - if they are on the surface.
 
Thanks for good wishes. This schratches are on the surface, that is on the CA layers. They are not touchable (surface is very smooth). I guess you could say that this are more of spiral lines than schratches, but can not be removed with soft paralell sanding (like we do with sanding marks after each sanding size). George
 
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