Burn out oven repair

In the mean time I tested my sodium silicate.  Measured out .01lb of SS and added it to .24lb of play sand for a 4% mix.  Mixed sand with a plastic spoon on a paper plate.  Nuked for 60s, 30s,  cooled, then another 120s.   Total 3m 30s.

Results were very good.  Wonder why it did not work well last time I tried it.