In response to the query about a GMS which doesn't use chromic acid, the
stain can be done with periodic acid, as in the PAMS stain, but the results
are less intense.  Also depending on the organism being stained, because the
periodic acid is not as strong an oxidizer as chromic acid, you may find
that specific organisms or fungus will not stain or stain as well as with
chromic acid.
        If you are doing a GMS in the microwave oven, you can decrease the
percentage of chromic acid to 2% and it can be reused until the orange color
begins to turn brown.  You can also preheat 2 percent chromic acid in a
paraffin oven to 55 degrees C and then add the slides, incubating  the
slides for the original one hour and you will have better oxidation.
        I hope this helps.  Cheryl