sometimes answers to your own questions pop up in unexpected places.....

Found this on APARTMENT THERAPY   which is exactly what i want to do....

Here is the product itself ; FABRIC ETCH   that you apply to the fabric in whatever pattern you like, iron & then wash out & it will 'etch' into the fabric , leaving the 'watermark' effect that i am after...

Once i have given it a shot I will post a few pics (if i am successful that is...)

Thanks for the suggestions Chris,

I like the watered down acrylic idea - will buy a yard of the fabric and give it a try... Dunno if i am uo to the screen printing....  

the curtain is going to be approximately 12' x 10' with large bamboo imagery - either that or several large fleur-de-lis... still in the decision making process...

Do you want to do one big image or a repeating pattern?

If you want one large image, watered down white acrylic paint would change the transparency. You could also use ink made for fabric (like for silk screening), which might do better as far as texture. Hanging your fabric and using an overhead projector will help get the design just right.

You can certainly add a repeating pattern, as well, but you'll need to use a stencil (with lots of care) or embrace printmaking. Gocco would do well for this project, but they're getting harder and harder to find. Or, you could take the plunge into screen printing...here's a tutorial I wrote to get into it on the cheap. One warning: once you learn, you can't stop.