Success? Slip Cast Holes using Wax Pins 

Great point about the drills and yes that is an interesting thought! It's worth a try to see what happens.

I think the trick with casting one's own would be getting a good surface finish so the geometry didn't pose any retention issues. And as with the other comments about adding a head - it wouldn't be that helpful for all of the orientations needed and if the tolerance was ok like my last videos I could just place it in the right spot.

Any ideas for sealing off the cut end as well?

Thanks! Yes I thought about that as well. However I'd need to get the tolerances correct first since some wanted to slide out and a blob on the end of the outside wouldn't help for them.

I was able to get a good seal in previous attempts with the right size hole - no need to use a cone.

The problem would be whatever plug the tube isn't PTFE and that would likely retain the slip so kinda defeating the purpose. As far as pulling through, my previous attempts had a decent tolerance and friction was enough so I think that is the real solution there. And even if not, no the outer mold wouldn't work since that is flush with the plaster surface. Pulling the pins from the outside wouldn't work since there isn't anything to get a hold of just as I had issues here with the wax pins that ended up flush.

Thanks for the ideas. I don't think putting anything inside to sand the surface would really work. Either with the static friction it would just roll (and not sand) and if you had something heavy enough to impart force, I'd worry about cracking the bone dry piece.

I was originally trying to make them when it was leather hard and my clay body wasn't happy which lead me here (I've got several other videos on that). I don't think I have the patience to do it when it's bone dry. I hadn't thought about doing it once it was bisqued.

The balloon would move to fill the area of least resistance.

That is a good idea. I'd need to make some good molds but then I wouldn't have the tolerance issue I had here in that case. And I could make them any size I wanted.

I have seen (dry) beans mixed into throwing clay to leave cavities as they burn out. It's a very rough look! I think part of that is due to the amount the clay shrinks. I'm guessing the same issue would happen here - the clay still shrinks.

Unfortunately it does not. And even if it did, that would be hard to do in the full sphere form.

I can't get to the inside of my sphere mold which is my target form.

I'm not sure if there'd be space for the clay to release in that case. When I use air for regular parts, the shrinkage of the clay is in my favor - pulling away from the plaster walls. Here the clay wants to constrict around the pins.

@@PotterybyKent I was thinking blowing canned air from the inside of the pot to just move the wet slip away from the pins before the clay shrinks away. Also wondered about the material you use to 3D print. Does that come in a spool? Would it be more consistently sized than the wax rods, and nonstick for the slip? Printing pins would be tedious, but might be splendid if the material works well. I’m a beeswax worker and would likely mold pins if the wax was the best option. Beeswax is durable and reusable. Alternatively, I use canned spray silicone on molds which would repel pretty much anything wet. Spraying your original metal pins should work well. One final thought on the metal pins is Plasti-Dip. There are both spray and dip options. It forms a long lasting chemical resistant plastic coating on tools, etc. it’s not expensive to try…

Ah I see. The newly formed clay is still very wet so any focused air blast could easily and inadvertantly disrupt the pot. I did briefly think about spinning the mold to get the slip off but didn't have an easy way to try that. Silicone spray was discussed in the comments previously and the worry there is about coverage and the coating coming off. Printing a pin wouldn't work because of the texture of the print (I have a 3d printed funnel and there is some slip that sticks to it). And the filament itself is too small to use directly. I'm not sure if it is slippery enough or not to shed the slip.

Because I need to get the clay out of the mold. Beyond that, the wax would prevent the clay from shrinking as it dries and would likely cause cracks.

I'm really looking for something closer to 4mm. I don't want to go below 3 for my particular use.

Also another idea - push the end of each pin against a warm surface to "mushroom" the end to a larger diameter, this'll keep it from going through the mold and it'll give you a bit of a handle to grab onto from the outside. For the tolerance issue, you might be able to make a gauge to sort your pins and eliminate the fattest/thinnest ones.

The idea of making one pin fatter is in another comment here, but that doesn't work since the orientation also matters with the pour tolerance. With a good one, it wouldn't matter.