Tiny bubbles in acrylic when sanding

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Jester4977

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Aug 31, 2019
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Hi all! First post here and I'm looking for help with my acrylic technique. When turning I get the pen to size and I don't see any bubbles, chips or imperfections, but when I sand I can start to see tiny pockets that fill with sanding residue and show like white dots. What am I doing wrong?!? I started with 220, then went to 320, where it is here in the picture. I'm new to turning, so I haven't yet built my skills up to start sanding at a higher grit yet. Thanks in advance!
-John

20190903_175315.jpg
 
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1shootist

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Did you make the blank yourself ?
It looks like tiny air bubbles from an improperly made blank.
I'm quite sure someone knowledgeable will chime in soon.
 

Curly

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Check other blanks and see if they do the same. If so it is something you are doing. If not it is the blank that has the bubbles. You can fix that one by applying CA after cleaning it to remove the dust and the holes will disappear.

Please note I am chiming in but am not a knowledgeable someone. I just play one on TV. ;)
 

Jester4977

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I bought this blank from woodturningz.com, and I have seen other blanks I've turned do this as well. I have seen others here talk about buying blanks from other members, how would I find members who sell blanks?
 

Jester4977

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Also, I find it impossible to get the white residue out of the holes. I've tried using water and brushing with a toothbrush, picking at them with a tiny needle, and also using compressed air. I can only get some of them cleaned out, but not many.
 

magpens

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I wonder if you are sanding circumferentially with the lathe power ON ? . If so, could be heat building up on the surface causing bubbles.

When I sand acrylic, I never turn the lathe on. . And ... I sand longitudinally ... turning the lathe spindle a little bit at at time with my other hand.

Not saying that this is the answer for you .... it's just the way I do it. . I don't seem to get those "bubbles" that you show.

I certainly sense your frustration and I know how hard it is to get rid of those white specs !!!
 

greenacres2

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I wonder if you are sanding circumferentially with the lathe power ON ? . If so, could be heat building up on the surface causing bubbles.

When I sand acrylic, I never turn the lathe on. . And ... I sand longitudinally ... turning the lathe spindle a little bit at at time with my other hand.

Not saying that this is the answer for you .... it's just the way I do it. . I don't seem to get those "bubbles" that you show.

I certainly sense your frustration and I know how hard it is to get rid of those white specs !!!
Heat was my first thought as well. Took me a while to be able to do Acrylic Acetate without bubbling during turning, sanding or both. I'm guessing your heat is coming in sanding, which is fusing the dust into the tiny holes--and the reason the dust won't clean out of them.
earl
 

ed4copies

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I would suggest sanding it through about 1000 grit, then look at it.

I expect the bubbles will still be there, but the surrounding material will be shiny, not all scratched.
THEN blow off the blank with a compressor, if you have one. THEN apply Boiled Linseed Oil while the lathe
is turning slowly. You hope the bubbles will then be clean. Let sit overnight, then apply the CA of your choice,
I would use GluBoost thin. Put on just a little then stop and look at the blank. I suspect it will start to look pretty
good--so continue with CA finish. When complete, sand and polish the CA finish and you will have a great looking
pen!!
 

jttheclockman

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Lets take this a step at a time before you go buying stuff . If this is a blank made by a caster then they did a terrible job casting if they are getting bubbles like this. That is first so think twice if you find this on other blanks that were cast by a caster. I am going to tell you this straight up, there are and getting more and more people casting blanks and they sell to vendors. If you or anyone else having problems with blanks from a vendor let them know. Their reputation is on the line too. Not everyone is good at it.

Now when sanding you need to slow the speed of the lathe down. Never sand as fast as you turned the blank. This is where a VS lathe really shines. But as you see on this blank you shown, you sanded with the lathe on thus the radial scratch pattern. After each grit stop the lathe and sand with the length of the blank slowly turning it by hand. Now wipe the blank off with denatured alcohol or a wet cloth with water. You want to clean the blank from any sanding dust from that grit of paper before you move on to the next grit. Rinse and repeat for all grits you sand with and also MM if using. Remember the golden rule of pen turning "HEAT WILL HURT" no matter what phase of turning you do.

Now you or many others will chime in here and say I do not have a VS lathe and it takes too much to change speeds. For those people I say learn to use a skew!!!!!!!!!!!!!!! you will not have to use sandpaper at all. If you can use a skew I suggest it on this blank and do not hit with sandpaper. Then use some thin CA and coat the blank filling in any defects. You can do this step if you can get the blank cleaned and you did not use the skew also. Do not build up too much CA because you are only looking to fill in defects. Then start sanding with Micromesh and use water as a lubricant. The first couple pads will be what gets the blank nice and smooth so be careful and run your fingers over to see if it is smooth. Then proceed with the rest of the pads. Good luck and this is my opinion on how to fix this and what to look for.
 

MRDucks2

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Do not hesitate to take the blank as you have it in the photo with you to Woodturningz. They are both good folks and experienced pen makers. They will quickly be able to give you feedback and will replace the blank if it is a casting issue.


Sent from my iPhone using Penturners.org mobile app
 

magpens

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@Jester4977

I bought this blank from woodturningz.com, and I have seen other blanks I've turned do this as well. I have seen others here talk about buying blanks from other members, how would I find members who sell blanks?
You asked about making contact with IAP members who make and sell pen blanks ...
Just keep an eye on the forums here. . People will advertise the fact when they have blanks to sell.
Just be aware that some member-made blanks look more professional than others. . You need to see pictures before you buy.
There are also plenty of nice blanks for sale by the various vendors that all of us order from. . If you need vendor names, send me a private message, or start a "conversation" with me and I can help you with that.

If you want to make contact with IAP members who make and sell blanks here are a few ways to do that.
There is something called "IAP Marketplace" under the "Forums" heading on the black bar above.
Within the marketplace, there is a forum called "For Sale".
And there is another called something like "Trades, Gifts, and Wants".

Some guys aren't too fussy where they put their ad, so you might find it in the general "Penturning" forum.
You could even write your own ad, as a "wanted to buy", if you want to.
 
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duncsuss

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Try wet sanding - might want to cover the lathe bed with something first (I use magnetic a/c vent covers that I found at Home Depot).

It not only cuts down the heat, but reduces the amount of dust that sanding creates.
 

MRDucks2

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I got my pits from sanding with too much pressure. Lightened up and the pits went away, lightened up a little more and most of the heavier streaks you see went away. Started wet sanding resins and the world changed when to came to finishing.
 

acmaclaren

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I've turned blanks from Woodturningz before and have seen what your are seeing. By the time I've gone through all my sanding, it has all gone away. I use WoodRiver-Woodturner's Mesh Sanding Pack. I go through all the grits sanding from side to side. I don't press down on the blank. I just hold the sanding mesh against the blank with the lathe on. Between each grit I wipe the dust off with a paper towel. Then I wet sand with my Micro Mesh pads. Between each pad I wipe the blank. Then I finish it with car wax.
 

Chasper

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I think I see tiny chips in an Inlace Acrylester blank, not bubbles. It tends to chip easy is your technique is not exact. Try using a skew for the final several passes, use a very light touch near the end. Super sharp tools would also make a difference. I don't think it has anything to do with your sanding technique, you aren't creating the pockmarked surface when you sand, you are just exposing it with the sanding dust. To fix what you already have I would first try using 220 grit sandpaper to attempt to sand them away. If that does not work then cleaning with BLO and using CA as a filler and finish should work.
 

pshrynk

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To clean the holes out, try denatured alcohol. It penetrates better and can clean stuff out. Then, a CA coating might smooth things out for you.
 

Jester4977

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Indianapolis
Thanks for all the great feedback! I'm still working on my technique, but have found that a skew makes easy work of rounding the blanks. I am also seeing that some blanks chip very easy while others do not, using the same technique and carbide tools. Most blanks I am able to CA and fix, but I just had one that I glued to the bushing and ended up losing the blank. Will just have to keep working at it.
 

WriteON

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Aug 21, 2013
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Lake Worth,Fl. / BlueBell, Pa.
Hi all! First post here and I'm looking for help with my acrylic technique. When turning I get the pen to size and I don't see any bubbles, chips or imperfections, but when I sand I can start to see tiny pockets that fill with sanding residue and show like white dots. What am I doing wrong?!? I started with 220, then went to 320, where it is here in the picture. I'm new to turning, so I haven't yet built my skills up to start sanding at a higher grit yet. Thanks in advance!
-John

View attachment 224893
Welcome aboard. Is this a new problem or just this piece? Maybe the blank came to you loaded with porosity or the white dots. And yes... all acrylics are not created equal. Some are extremely brittle and touchy. You’ll get this worked out. Experience is your best teacher. Sharp quality chisels are your best friend. Are yours new and sharp?
 
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