+# Batch 2019.06.21 #
+
+A total of 12 3" KNSB grains for 54mm cases. These were cast in two batches
+that each consisted of a two 9" casting tubes, one each with 0.5 inch steel
+and 0.625 inch Delrin cores. One batch was pure KNSB, the other was my usual
+mixture with RIO and Polystep-B1 surfactant. Simple pour, insert coring rod,
+top off grain. No vacuum processing or vibration.
+
+The 54mm casting tube I'm using weighs 1.9g per inch.
+
+The purpose of casting these grains is to do test stand burns of identical
+motors in each of the two propellant variants, so I can tell how much the
+RIO is affecting ignitability and burn rate.
+
+These grains were cast on 2019-06-21.
+
+## Results ##
+
+The batch size was pretty good, there was a bit of excess propellant in each
+batch so we can make density and burn rate measurements after cure. The excess
+weighed in at g after cure.
+
+Grains were cut, core drilled to 0.625", and sanded more or less ala Terry's
+process. In the data below, lengths are a bit approximate due to imperfectly
+squared ends, gross masses are precise using my new 600g by 0.01g scale!
+
+Batch with RIO:
+
+* Grain 1, " long, g gross, g casting tube, g net
+* Grain 2, " long, g gross, g casting tube, g net
+* Grain 3, " long, g gross, g casting tube, g net
+* Grain 4, " long, g gross, g casting tube, g net
+* Grain 5, " long, g gross, g casting tube, g net
+* Grain 6, " long, g gross, g casting tube, g net
+
+Batch without RIO:
+
+* Grain 7, " long, g gross, g casting tube, g net
+* Grain 8, " long, g gross, g casting tube, g net
+* Grain 9, " long, g gross, g casting tube, g net
+* Grain 10, " long, g gross, g casting tube, g net
+* Grain 11, " long, g gross, g casting tube, g net
+* Grain 12, " long, g gross, g casting tube, g net
+
+The mass per unit length was within ?g/inch.
+