Dots in crowns after pressing Emax

[Luis Quintero]

Hi, does anyone know why this little dots appear on my crowns when I press them?
I leave the cilinder 15min at 1000c° in the oven before pressing it with an automatic press furnace
It doesn't look like big deal in photo but the dots are very noticeable in person

 

[Car 54]

What investment are you using? What is the burn out temp and time at temp?

And when you say," I leave the cilinder 15min at 1000c° in the oven before pressing it with an automatic press furnace." Is that the pressing oven parameters or the burn out oven? 1000c is really hot, you may be cooking the investment and the ingot, causing contamination. Others here may have some ideas and advice as well.

I burn my MicroStar emax rings out @1585 Fahrenheit for45 minutes in the burn out oven, then into the pressing oven where they press at ~920c
These are the instructions for the older press oven, but the temps are still in line with the newer Ivoclar press ovens as well.

 

[Luis Quintero]

What investment are you using? What is the burn out temp and time at temp?

And when you say," I leave the cilinder 15min at 1000c° in the oven before pressing it with an automatic press furnace." Is that the pressing oven parameters or the burn out oven? 1000c is really hot, you may be cooking the investment and the ingot, causing contamination. Others here may have some ideas and advice as well.

I burn my MicroStar emax rings out @1585 Fahrenheit for45 minutes in the burn out oven, then into the pressing oven where they press at ~920c
These are the instructions for the older press oven, but the temps are still in line with the newer Ivoclar press ovens as well.
View attachment 45175

Hi, sorry for bad English
I mean I leave it at the burn out oven at 1000c and then at pressing oven where they press at 915c for LT
I normally leave it in the burn out oven at 900c for 15min right after it gets to 900c
As far as I remember I elevated the temperature due to the dots in first place, I thought it may be some wax residue or something due to ambient temperature being cooler this time of the year
But thanks for the advice, I'm going to try it again at 900c and see if I was cooking the investment as you said
Also I'm using an investment named SmartVest Press

 

[Contraluz]

Hi, sorry for bad English
I mean I leave it at the burn out oven at 1000c and then at pressing oven where they press at 915c for LT
I normally leave it in the burn out oven at 900c for 15min right after it gets to 900c
As far as I remember I elevated the temperature due to the dots in first place, I thought it may be some wax residue or something due to ambient temperature being cooler this time of the year
But thanks for the advice, I'm going to try it again at 900c and see if I was cooking the investment as you said
Also I'm using an investment named SmartVest Press

The high temp for burnout is 850 Celsius! 1000 is waaaaay too high! Follow the instruction of the investment!

What wax do you use? Is it a wax meant to be pressed? Some wax are not as pure as one would like to. There are special waxes meant to be used when pressing ceramics.

 

[Luis Quintero]

The high temp for burnout is 850 Celsius! 1000 is waaaaay too high! Follow the instruction of the investment!

What wax do you use? Is it a wax meant to be pressed? Some wax are not as pure as one would like to. There are special waxes meant to be used when pressing ceramics.

I use Geo Crowax in grey opaque from Renfert and sometimes a more economic one called Filenes

 

[CatamountRob]

It seems like I’ve read that opaque waxes are not ash free?
I’d probably try a different wax.

 

[Car 54]

It seems like I’ve read that opaque waxes are not ash free?
I’d probably try a different wax.

Good point, as it seems to be a sporadic issue, depending on the wax used?

 

[sidesh0wb0b]

Hi, does anyone know why this little dots appear on my crowns when I press them?
I leave the cilinder 15min at 1000c° in the oven before pressing it with an automatic press furnace
It doesn't look like big deal in photo but the dots are very noticeable in person
View attachment 45171View attachment 45172

make sure your plungers are clean, and the access hole for the plunger is clean and free of debris as well. it looks like little bits of investment are being pressed into the crowns.
could also be when you're turning the ring over to drop in the ingot and plunger, be sure your surfaces are clean too.

 

[Patrick Coon]

When was the last time you cleaned out your burnout furnace? I would vacuum them out at least weekly. Residue from patterns or dust can build up in the bottom of the furnace and with convection from the heating of the oven, the carbon (from the burning of organic material: i.e. wax and resins) can be lifted from the bottom of the furnace and blown up into the ring. Also, there is no reason to heat your plungers (in fact it is not recommended) and putting them in the furnace can again allow the carbon from the bottom of the furnace to contaminate the end of the plunger that is going into the ring.

 

[Gru]

From the single press pic I'd recommend following all of the above recommendations, plus calibrate your burnout oven and also cleaning the burnout vent. It also would appear your pressing has an "orange peel" surface texture which is often too hot as well. Your Alox plungers need not be heated beyond the manufacturer recommended burnout temp (which must line up with Ivoclar's e.max burnout recommendations). Oh, and if you're heating the ingots, that's not ok either.