hi all its been a while but for greywash i tend to use distilled whichazel which works well for me. You can buy it at any chemist or wilkinson store for a couple of pounds. never had problems with any reactions.
Heres how i do it
3 ink cups
first one with half black half witchazel
second cup 3 drips of black toped up with witchazel
tird cup 1 drip toped up with witchazel
Make sure you mix it well or it will show up white on the skin
works well for me
i find that it personal preference, I use distilled water, i also use kuro sumi grey wash only and feather it out, or cross hatch, witch hazel will give a different Flo, it's just down to preference tho i would stay clear of tap water, no other reason than to cover your ass!
needle use would also make a difference along with machine set up, i now use a swash drive rotary for shade, slow!!! less trauma so i can build, generally i use a curved mag. or weaved, and rarely a circular motion!
There are lots of answers to this ? but the best is to find what suites your style, from all of these! that's my 10peneth
Ive tried every trick under the sun and found that for me the very best is a mix of 50/50 pure glycerin and witch hazel still sterile due to the witch hazel and the glycerine gives it some thickness so its not so runny