[SML] DIY flame retardant?

[jdunfee12 at yahoo.com]

I originally sent this yesterday from another account, but for some reason stuff from that account never makes it to the list. I had forgotten that the reason I re-subscribed via Yahoo, was to work around that limitation.  Anyway, here is it is again;-----
I am planning for a production of Rumpelstiltskin, and the pile of straw, to spin into gold is one of the items needed.  Since I am in a Amish area, there is plenty of hay being grown locally. So, I can get hay, before it gets scrunched up into a bail.  Then, I can do a more traditional type of bundle.  But, I do want to do some flame retardant. 
I've seen plenty of recipes for DIY folks, that are obviously much cheaper than the commercial formulations, if you plan to treat much volume.  I've read that the Borax + Boric acid version seems to work very well, even when compared to commercial products. There is also a place with curtains made from black cotton bed sheets, and I would like to treat their curtains as well.  So, I am looking for advice, in terms of the end result.  I've read that the 6 part, Borax + 6 part Boric Acid + 100 part very hot Water can leave crystals on the fabric.

I've seen other variations on the Borax + Boric Acid ratio, and ones that use other chemicals

1) 6 part, Borax + 6 part Boric Acid + 100 part very hot Water (some say 6 part Borax and 4 part Boric Acid)

2) Mix 1lb Alum, with 1 Pint hot water.

3) mix 1 cup ammonium chloride with 2 pints of water.  Then, add 1/2 cup ammonium phosphate.

Even with a risk of crystals, it sounds good for the straw, and I can get the chemicals at local stores.  But, am I wasting my time, if I attempt to use the Borax + Boric Acid on the black bed sheets?

I have been unable to find any comparison about the other approaches, such as version 2 and 3 above.

Any other advice?
-Joe
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