I have my castings fixed and wanted to share just what worked after receiving so much help here, and from reading others problems and tricks. I took some time and called Satin Cast to talk about the temps that are being suggested on Monday, and the breakdown of the investment along with other problems I was having. I spoke with Philip Read Product Manager and the one thing he made clear was no matter what your oven says on the outside on a temp gauge, it should not go over 1350-1375 (inside flask) at its core as the investment will break down, crack, and discolor. All of what I have always knew (and I’m sure most of you did too), and thought that seeing folks here taking temps up that high satin cast could take the heat and my problems were something else. My investment was breaking down thus having awful castings.
Philip and I spoke for about a half hour and at the end of the conversation he was sending me out at no charge some of his SATIN CAST DIAMANTE, saying that if folks were using high temps best try this investment. Looking forward to casting it higher, but honestly see no need.
He also wanted some samples of the cherry resin, and a completed resin model so they could try it out and see in their lab possible what the best would be for us.
I have had beautiful castings after making some minor tweaks and going back to the same way I cast lost wax with some small changes. My castings are now coming out like they have been tumbled and have a smooth bright sheen to them. I am not saying this will work for you, but I can say that your castings are looking just like mine did when I was tinkering around with no luck and after I was breaking down the investment, then hope this helps.
I used Clean Cast White #242 from Stuller.
1. I added an air pump to my oven to help push air into the oven.
2. Mixed satin cast a little thick for 3 min, vacuum for 3 min, pour into flask and vacuum 1 min. let sit 30 min without moving it. I also used very warm water.
3. Flask sat in oven off for 4 hours+ before it turned on.
4. Oven temps on control 300 @ 2 hr / 700 @ 2 hr / 1350 @ 3 hr with 5 degrees per min ramp on each stage. About 11.5 hour burn out.
5. Flask size was 2.5 x 3.75
6. Raise flask off base of oven floor
7. Once the oven finished I go by my outside control panel for temp and cast when it says 500-600, this takes 2.5 hours from 1350.
8. I'm using a electro-melt and my metal is ready to go when that temp is reached, and I then move to vacuum caster and pour.
9. Let sit for 5+ min and quench
Note: I used a UV nail lamp box to cure my resin for no less than 4 hours.
I am not going to speak for others who have had great luck casting so hot, but for me it only made my investment break down and have porosity in all metal types. I have had discoloration in my flask from resin melting out, but it has not affected any of my castings.
After speaking with Philip at Kerr my suspicion was correct and raising the temps on the investment above 1350 was killing my castings, and tinkering is what got me in trouble with my castings over these past few weeks thinking it was not getting hot enough. One thing I feel is very true like Robert and akgold (and others) have been saying is airflow, airflow, airflow and knowing your temps in YOUR oven, and when to cast that flask and how when it’s the correct temp.
The only thing I really did to get back to something that was consistent with lost wax, was raising my time a bit longer, air flow, raising flask off the bottom of oven, and casting at a temp that works for my oven, when reading the temp on it….that being 500-600 while the temperature on the inside of my flasks were closer to casting temp.
The on picture of the two rings is of a 50/50 new gold old gold just to see how the castings would work with my setup. All in all nothing a emery stick can’t fix and still came out great and took these photos right after I got the investment off. The single ring is all new clean cast #242 gold.
I have been holding out on my more complex designs until I got this down and will post some photos of those soon.