Bubbles follow-up

[08K.80]

I asked about holes I found in some blanks and it was determined to be bubbles. I didn't take any pictures of the first blanks that this happened to, but I received more blanks and I remembered to take pictures.

These are not my casts and I haven't had this in any of my blanks I've turned. That is why I asked if it was normal in my original post.

When I received the blanks, I wanted to see what they might look like, so I sanded (no cutting) the outside off and this is what I found about 1/16" - 1/8" below the surface. More of the holes. Is this really caused from bubbles and is it really normal or common?

I rotated the blank to capture most of the holes, but these go all the way around and the length of the blank. See the red circles.

 

[reiddog1]

It happens sometimes. Trying to time the pour and keep color separation makes casters wait to pour as the resin is starting to thicken. While this makes for good swirls, it sometimes causes small bubbles that don't make they're way out of the blank. Fill the holes with some thin CA and sand as normal. Should take care of it. Sometimes, I'll do a CA finish on the blank if there's a lot of them. Nice blank by the way. Hope this helps.

Dave

 

[08K.80]

It happens sometimes. Trying to time the pour and keep color separation makes casters wait to pour as the resin is starting to thicken. While this makes for good swirls, it sometimes causes small bubbles that don't make they're way out of the blank. Fill the holes with some thin CA and sand as normal. Should take care of it. Sometimes, I'll do a CA finish on the blank if there's a lot of them. Nice blank by the way. Hope this helps.

Dave

So you are saying this is expected and acceptable?

So pressure actually doesn't work?
I don't use pressure and haven't found anything like this so far.
I could deal with one, maybe two small holes, but these are pretty big and seem to be throughout the entire blank.
These are the only home cast blanks I've used, other than my own.
This could have made a nice kitless.

 

[BSea]

So pressure actually doesn't work?

Many people think that pressure will eliminate bubbles. Pressure will reduce the size of bubbles, and helps prevent new ones from forming. Sort of like when sodas are under pressure, and you open the top, bubbles form. But reiddog1 is absolutely correct that bubbles sometimes happen. And the more colors that are introduced, the more chance for bubbles. Also, that blank looks like it was poured vertically, so the bubble that may be at the bottom, sometimes don't have time to get all the way to the top before the blank sets up.

I could deal with one, maybe two small holes, but these are pretty big and seem to be throughout the entire blank.
This could have made a nice kitless.

Are these alumilite blanks? The reason I ask is that you said kitless. And even though you can use PR for kitless, it's pretty brittle when it comes to turning threads.

 

[PSNCO]

I got those on a lot of PR pours when I first started out. They especially form if you pour and one of your colors start pouring like taffy. I got them when I would run a wire down the tube the PR was like taffy already. I got a couple blanks like that from pours this week where I preheated my pvc tubes in front of my portable heater. The pours were karo syrup consistency, but the PR set quickly when hitting the VERY warm PVC tubes.

When it happens, i just cross my fingers and hope the bubbles aren't too deep. I've also gone back on some blanks with the deep holes and poured in resin with a like colored resin.

 

[08K.80]

I would have to ask the caster about the material. When I was sanding, it smelled like polyester, but I don't know what Alumilite smells like.

I use PR to cast, and I have threaded a couple of them without any problems. Maybe I just got lucky?

 

[Marko50]

I haven't noticed any smell with Alumilite. Not when casting, turning or finishing. It's one big reason I love using it.

 

[Hendu3270]

Like has been said, pressure makes the bubbles smaller. FWIW...I have found that the "top surface area" makes a difference. A blank poured in a round mold and set upright to cure has only the diameter of the blank for bubbles to escape from the blank and some bubbles must rise the entire length of the blank. Whereas a blank that is poured in a rectangular mold laid out on it's side, has a much larger top surface area where the bubbles can escape and they only have to rise a short distance. This is my experience only. I really like using pvc pipe for molds but I just haven't been able to minimize the bubbles enough to make it worth it for me. I built a mold from a cutting board and can get three blanks out of it.

 

[JohnU]

Like said above, pressure reduces air bubbles but sometimes they are still noticeable. It's not uncommon to have air bubbles along the edges of the mold, especially if there were reminents of prior castings stuck to it, for air bubbles to get hung up on while rising to the top. These will still make beautiful pens. Just clean out the sanding dust and wipe them down with some Denatured alcohol after final sanding and prior to a ca finish. The ca will fill those clear and they will blend right in and be unnoticeable when polished.