I used bog standard fabric softener to pre-treat my fabric at 2 concentrations, neat and 50/50 with water. I just dunked my fabric in the fabric softener so it was all coated and then left it to dry. I printed directly onto the dried fabric and then washed the fabric (i used cold water in this test) to see if the ink stayed.
And i'm very pleased to report that it did :)
Both concentrations worked, i treated 2 bits of fabric for each concentration and ironed one aswell after i had printed on it, but that didnt seem to make any difference, in fact it may have been detrimental.
50/50 fabric softener and water, top piece unironed, bottom piece ironed
Neat fabric softener, top piece ironed, bottom piece unironed
The neat fabric softener made the fabric a bit crunchy after it had dried, it was fine once it had been washed though. But, as there doesnt seen to be a difference, i'll use the 50/50 mix in the future.
I think i need to check how well the ink stays after washing with warm water and soap, possibly even through the washing machine aswell, but im really happy with the results!