to seek help on a geeky question...mordants???

[Standingonlego]

DS2 needed yellow t-shirt for random dress up day tomorrow. Shops shut, panic set in when DS1 had a genius idea. Dye it like he did at forest school...with tumeric in hot water. It worked a treat on a sad old white polo shirt - felt like craft mum! But now colour is still leeching a bit as i rinse and apparently i should have used a mordant...????

I am worried sweaty DS1 will turn yellow tomorrow...is there anything I can do now to help from the cupboard (cream of tartar? Bicarb? Vinegar?) or do i put a vest on him and hope for the best?

Any thoughts or insight dye and handicraft literate folks????

Salt fixes dye
Rinse in very salty water
Then in clean water

Urine's a mordant too, isn't it?

Tumeric is a dye hat doesn't need a mordant - look here

Just wash it a few times

Thank you folks. will keep going with the wash and rinse

It might not be terribly colour fast as natural dyes work best on protein fibres such as wool and silk. Cotton and linen are plant fibres and usually need a fair bit of treatment before dyeing using tannin and alum. If it has taken some of the dye and doesn't bleed a lot when rinsed, you can probably get away with a day's use tomorrow. He might look a little extra yellow but wont come to any harm

Wasn't Mordant a character in Lord of the Rings?

Bung it in the machine with a pound of salt, job done.

Thank you saltakatten for reassurance on the potential yellowness.
coolaSchmoola I will see what salt we have about