Jokester said:
Their solvent based so that they dry out quickly when used on paper.
Someone tested different colours on the forum a year or two ago by basically taking the felt out and dumping it in a jar of water to let it leech out before putting it in their loop. Obviously stainage is a problem but I don't think that's any different to the proper stuff.
Jokester
I used the same method for my loop.
Soak in small amount of distilled water for 24 hours to get a nice concentrated mix.
Then add to your loop till you get the desired effect.
I used flourescent yellow and it worked well with cathodes.
And from experience it didn't stain the pipes or the res.
The UV additive i have used before turned the pipes cloudy/milky.
Cheers,
Mark