Lost Wax

I am not sure I understand exactly what is getting made here.
The hook/wax is rather confusing, as is the plaster cup thing.
You got me head scratching.
What exactly are we making here?

 

Wax is for use of molding or shaping and then dipped into a slurry, dusted with silica sands and then hung to dry.
This method is repeated 4-6 times and again, allowed to completely air dry.

Once dried, the wax is removed from the ceramic shell via heat / flame leaving a mold of the desired future casting.

Once the wax is extracted the ceramic shell then needs to be fired off to burn out any remaining wax within the shell & allowed to slowly cool.
Blow out the interior of the shell with compressed air to remove any possible ash or trash from inside it.

The POP mold cups are just "that" as illustrated above, Molds for making sprue filler cups.

The hook is removed after the ceramic shell has air dried and before firing off.
Then the middle of the wax filler cup is basically hollowed out as much as possible before going through the lost wax process.
You want enough wax meat left so the entire shell can be placed upside down for Lost Wax removal.

Refer to Jason's Dog thread in the Ceramic Shell Casting section as he has a video of the entire process.

 

That's the ticket. Barry at outback foundry works on a granite slab.

Pat, he's made a system to make wax pouring cups quickly.

 

All of my ceramic shell casting will be done in an AC-ed controlled environment so I don't think I'll have any issues but if slurry dipping and shell making is going to be in a hot garage/shop you more than likely do NOT want to use the threaded hooks.
A hook or a piece of All thread with a couple of nut's & a washer on the end will be more applicable.
Off course you'll need to bend the exposed end to create a hanging hook.

Some Jason mentioned and he is correct, in a hot environment the wax will soften up a bit and the weight of the ceramic shell may very well be too much and cause the hook to break free............

Humpty Dumpty sat on the wall.....................

Murphy's Law.

 

Not exactly understanding the first part of your question so dummy it a little for me.

I haven't tried a regular ole cup in the attempt to make sprue wax cups/plugs.
Now the cups I used for making the POP mold might just work as they are for mixing epoxy resins and such in them and I haven't found anything to date that does permanently stick to them.

I'll have to try one out to see.
Regardless, you can't skip the ice bath after pouring.
The wax cups/plugs needs to harden and shrink to release.

If you were using a plastic cup as a mold & Not the water saturated POP molds I don't see any reason why you couldn't stick them in the freezer to harden and release.

The POP molds have to be submerged into a vat of water so they can absorb the water which creates a barrier that the wax won't stick to and will release upon shrinkage once submerged into the ice water.

About 20 minutes of pre-soaking should be fine but it all depends on how thick your mold walls are.

Best thing to do is have a extra dry mold and compare the saturation color of the soaked one to the dry one to make sure your good to go.

I hope this has answered your questions.

 

Kelly, was your questions directed at me or Jason, or just in general?

 

After chewing on this some my answer is, No.

Reason being, the large filler sprue which is attached to the sprue cup needs to be hollow to allow quick and rapid exit of the rest of the wax within the ceramic shell.
You want as minimal wax as possible within the ceramic shell due to expansion and cracking issues.
Ideally, if you have the technology to cast hollow wax structures in one shot (filler sprue cup, filler sprue, riser's etc.) that would be the ideal process.
I saw a video not to long ago where that is exactly how they did it but it was in a industrial plant with all the proper equipment to do so.
If I recall correctly, it was along the process of Blow Mold.

So, today was a microcrystalline wax day.
I wanted some concrete answer and did a few tests today with various thing of this subject and my conclusion and results are as such.

In a earlier comment of mine I mentioned something about possibly using the above shown chemical resistant mixing cups as cup molds.

This is one of the tests I performed today along with various other aspects of POP cup mold water absorption, timing and other observations relating to this subject.

Observation #1

I took 1 of the POP molds and weighed it dry.
The mold weighted 700 grams.
I then removed it from the scale and filled it with tap water to the brim.

The walls of these particular molds are 1/2" thick.

At the 2 minute mark the entire walls were completely saturated.
The bottom portion of the mold was not.
At the 4 minute mark the bottom of the mold was saturated as well and the sides of the mold was showing water beads on the exterior.

I re-weighed the mold after complete saturation and it weighed 845 grams.

Additionally, the water level within the cup had dropped by 3/4".
Note in the picture the color difference of the dry mold vs. the saturated mold.






Observation #2

I placed 3 POP molds in a pan of cold water.
As you can see, air bubbles were emerging from the sides which indicates air being replaced with water absorption within the mold walls.
As noted above, it only takes 4 minutes for the entire mold to become saturated completely.
After 4 minutes I stuck a frozen bottle of water in each one to chill the molds.

While water within itself helps create a release barrier from the hot wax and the mold walls, ice water in it's self does nothing more than accelerate the cooling and complete release phase.

In fact, all that truly needs to be done when making these wax cups is make sure the molds are completely saturated with tap water, pour and let cool at room temp.
Once the wax has (completely) solidified, the wax cups can be lifted right out of the molds.






Observation #3

Wax was heated up and the molds were filled.
Do not turn your burner plate off at this time, keep your wax heated and melted for additional pouring.

As they started cooling down (however long that was) I noticed some severe shrinkage taking place and bad cracking developing around the hanger hooks.
More hot wax was poured into the voids and the molds were filled a little more.

I left one of the pour untouched and after the surface of the wax cup had solidified, I submerged it into the cold water bath.
Upon removing the cups from the bath it became evident that the crack/void had ran much deeper than just below the surface.
In fact, approximately (1/2) - (1) oz. of water ran out of the void.
Although this wouldn't really matter or affect the final out come of the casting inn itself, it may very well be an issue with properly being able to keep the hanging hook anchored and support the weight of the ceramic shell (slurry & silica sand) required to create the shell.

Side Note:
Once the ceramic shell has been completed and is ready for firing, the hook will be removed and the inner section of the wax fill cup will be carved or bored out for extraction purposes.
Remember, the less amount of wax and the more voided area you have within the shell will result in the better chance of ending up with a un-cracked fired / finished shell.






Observation #4

As previously mentioned above, it is NOT necessary to submerge the filled molds into a ice bath after pouring to get the wax filler cups to release.
They will do that naturally on their on in due time, approximately 4-5 hr.'s in and AC-ed room.
The ice bath only accelerates the solidification of the wax and release stage if your in a hurry.

The POP molds "DO" have to be saturated with water prior to filling with wax though.
********************************************************************************************************************************************

I also played around with making some hollow filler cups as well.

Saturated 2 of the molds, filled them 1 at a time with wax and then sat them in the cold water bath to accelerate the solidification of the wax along the interior of the mold walls.
I left them in the water until there was a thin filmed layer of solidified wax on top.
I removed them at this point, wiped dry the side and QUICKLY poured the remaining un-solidified wax back into the pitcher with the rest of the melted wax.

Do not try continuing to hold the mold upside down trying to get every drop of remnant wax out of the mold as the mold walls are still water saturated and water will start draining from the walls the minute they are removed from the bath and end up dripping into your wax pot even after wiping them with a dry towel.
Flip over quickly, dump melted wax, flip right side up quickly.

I did submerge these into the cold water bath and they popped right out of the molds within minutes.








Last but not least....

I wanted what kind of results I would end up with if using a chemical mixing cup as a mold.
This pour was allowed to cool until only barely warm and then submerged into the cold water bath for approximately 10 minutes.
Upon removing it from the bath, the wax cup Did Not release itself from the cups walls being used as a mold.
I then placed it on the counter top sideways. pressed down hard on the cup walls and rolled it back and forth.
This broke the wax cup free from the cup walls and came out nicely.

In fact, it was the smoothest and nicest cup produced out of all the filler cups short of the shrinkage cracking which developed during the casting process.
No big deal, it can be filled in at a late time.





In conclusion, one other item I would like to mention.

If your just getting into wax work, Do Not do this.
Only melt enough wax in your pitcher / container to fill approximately 3/4th the way full and make sure you wipe the excessive wax off the side of the melting container after you pour and before replacing the container back onto your burner.

After I realized I melted tooooo much wax in my pitcher, I removed some before pouring the filler cups.

It's also a good idea to wear leather gloves when handling / pouring hot wax.

 

Verrrryyyy Interesting........... What was the pouring temp of the wax during all of this?

 

210* lol

I know, I know

I got busy with setting up............

 

Kelly,

Here's something that I think runs along the lines of your questioning/thinking.
Can't find that other video I mentioned earlier. I'm a still looking though.

 

Moved to the appropriate thread.