Has anyone any ideas as to the darkest 'black' that will show up on a dark tshirt?

Looking at Tanith's color chart at the bottom of http://tutortanith.com/charts/rgb2cmyk.htm there's a black on the far right bottom.

One in to the left of that is a shade of black that is #333333

In my graphics programme text of that color shows up quite nicely on a black background. Is it the same in real life? Would text of that color be discernible on a black tshirt?

If so, I'm thinking that text of that shade could be used on light, dark and black tshirts.

Am I also right in guessing that this shade will be printed on top of a white underlayer for black tshirts?

I am not sure about the darkest black, but I had a dark BLUE that didn't really show up on the black t-shirt so I am very careful of the colors I use on black now. It was probably the 330099 shade or something close to it.

I don't know of any way to tell. There are two factors at work here. First we don't know what kind of black the shirts are. It is likely that that will differ significantly between shirt types, and at least somewhat even within shirt types. Second as noted in this article
http://tutortanith.com/imagecolor2.htm
I haven't a clue as to how black the black must be before they do not include the white underlayer. Whether it does or does not have the white underlayer will make a difference in how discernable color is.

I know a few people have experimented. An even bigger problem is that it is nearly impossible to be truly wysiwyg between the screen thumbnail and the actual product. You won't rally able to tell, but more so your customers won't. Something that looks distinctive enough on your local machine may lose that distinction when shown in the thumbnail, or worse it could sharpen that distinction but not appear in the final product.

If I seriously wanted to do a project like that I'd create a design similar to http://tutortanith.com/images/colors/blacks.png, perhaps adding more star points with lighter and lighter black variations then order a shirt and see what happens. When I test I like to make the test wearable - so if not geometric objects then maybe various shades of black cats being chased by black dogs or ravens or ghosts flying over darkened houses or ....

Thank you both for your reply.

At some stage I'll conduct experiments, but until then I'll keep my colours on black as un-black as possible, if that makes sense :-)

It's difficult, not being able to judge accurately what will and what won't show.

The third grey in from the right is a #666666 darkish silver. That shows up quite nicely on the light Tshirts. Surely that will show up on the black T-shirts?

I'm a little bit doubtful now :-)