We recently have casted a couple trees that keep coming out with the same casting defect and I was hoping to tap into the Ganoksin community to narrow down possible causes.
I’ll put some photos below, but the issue is small streaks/lines appearing after casting. These aren’t visible on the wax injections, so it is somewhere between investing, burnout, casting, and quenching. My guess is something going off during the investment process.
We have been using this process below before and it has come out fine, but these are chunkier rings than we normally cast. Also, it seems in general the surface is rougher than it was coming out before.
Details of our setup:
Using a Neusprue for the trees and riace wax for the injections
Using a vacuum investment mixer
Prestige Sigma investment powder (using sigma recommended powder:water ratio
Bench cure flask for 2 hours
Steam dewax for 1.5 hours
Burnout following Prestige Sigma recommendations (photo below)
Vacuum Cast brass at 1020 C with flask at 650 C (as per alloy recommendations)
Reminds me of flashing, but only the beginning of it. I would try increasing your bench cure time to 3 hours instead of 2, and lowering your flask temperature. You can also try increasing your investment ratio a bit.
I cast my silver at 1010 and my flask is at 530, 120 degrees lower than yours but the metal is only 10 degrees cooler. Basically you want the flask to only be so hot that you don’t get frozen fills. And you want the metal just hot enough that it fills completely then freezes. With thicker designs you can lower temperatures.
Those are water trails. They happen after the investment is poured into the flask but before it sets. I’ve noticed them when there was too much water for the amount of powder, or when they weren’t mixed thoroughly enough. Excess water makes its way up the sides of the models on its way to the top of the mold. Try a thicker mix, and mix it more before pouring.
What Awebry said. I showed this to my husband who is the expert in casting in our studio. He looked at the photos and immediately said “The investment is too thin.”
Definitely water trails. To completely eliminate the investment problems due to incorrect ratios , we use a food processing digital scale that does Grams, Kilo’s and Pounds. DSW-100 Portion Scale with Single LCD Display ($145 Amazon) . The water and investment is weighed in Grams. This scale will handle up to 60 lbs accurately. The Spring scales that are sold to the Jewelry trade are often inacurate as the springs lose their strength.
Be sure to keep things working during your whole 8 mins working time. Mixing vacuuming, pouring. Don’t finish these things early before the investment is close to setting. If The investment sits very long without mixing the water will separate and run down the side.
