I have found a company that sell Hydrochromic inks, please see document below that was forwarded via email:
Polysccorp™ HYDROCHROMICS
Hydrochromics is a new concept in color changing technology.
The screened image is activated by water or humidity. A white hydrochromic ink is screened over an image. All you see is the white ink. When water is applied to the white ink, it disappears and the image behind it appears. When the water dries, the image goes back to white.
* Color : White, Red, Blue, Yellow, Green, Pink
* Application: Screen Printing
* Curing: Can air dry but advise forced air/heat combination as through heat tunnel commonly used by shirt printers
* Substrates (Potential applications) - Soft sheet vinyl, Papers, Coated papers, Styrene sheets, some Polyester fabrics, Soft PVC
* Coverage: 20,000 square inches / Kg
* Recommended Screen Mesh - 64 mesh monofilament, 1 pass=2ml
* Ideas – Rain Coat, Beach Ball, Umbrella, Wallpaper, Place Mats, Greeting Cards, Decals, Poster
Ink is ready to print and easy to fix on fabric by heat drying, detailed technical information will be followed with your ordering ink.
Price of Hydrochromic Inks are as follows :
Q'ty(Kg) Price / Kg, USD, FOB
~ 50 220.00
51 ~ 100 195.00
101 ~ 250 175.00
251 ~ 500 157.00
501 ~ 750 149.00
751 ~ 1000 137.00
Payment :
Payment : T/T Advance by Bank Wire
Delivery : 14 days upon receipt your T/T Payment
As you may see our "Sales Policy", Samples are available for your evaluation test with Euro 2.0 / gram by collect below 1 Kg.
Best regards
S.K.Park
CTO
PSI Korea
+82 10 8736 0077
I haven't ordered any inks and have not been able to find any other supplier, it might be worth contacting a company like Matsui.