Dear Paul, that sounds interestingÖ
Iím sure you do know how to extract hexamine out of ESBIT, itís not difficult at all. But I would prefer buying the pure hexamine powder, itís not that expensive (at least here in Germany)
Reading the Unicolor MSDS they claim their stabilizer is hexamine at 100%, so if you got the correct weight (about 5g/liter) it should work fineÖ
But in some stabilizers is another antifungal / biocide present (about 20 times less concentrated than the hexamine), Kodak and Tetenal are using 1,2-Benzisothiazol-3(2H)-one, CAS: 2634-33-5 in some products too.