I have tried Varathane 900 a varnish that performs as a semi-color preserver and really like the look. It allows the thread to darken and go translucent but preserves a little color (though darker than the original). Other varnishes basically allow the thread to take the color of the blank underneath. Is there any product other than the Varathane which will give me the same look in a water based product sold in a small bottle for convenience?

i have some experience with water based polyurathane as a color preserver but i don't think that will get
you exactly where you want to go. three coats of olympic water based poly and i have an opaque wrap that is very close to the spool color. varnish overcoat does not darken it any more. you might want to pose this question on clarks classic bamboo site. those guys have some experience getting the most out of varnishes and color preservers. you will have to register to post on the site.

In playing around with silk I tried clear nail varnish, thinned with isopropyl alcohol. Didn't go with an exact ratio, but enough alcohol to turn it milky without separating the solvent and solute. Probably in the 3 (varnish) to 1 (alcohol) ratio. The mix is watery, and settles after a couple of days. I shake it up, apply a flooding coat and let dry. When it does dry properly it's only a shade darker than spool colour, and no transparency. More noticeable after a couple of days.

Gudebrod one part finish #840 gives alike effect, the thread doesn't darken as much as it does with epoxy or Perma Gloss

Pavel,
Moscow, RU

Varathane Crystal Clear Diamond, blue can, will give "off-the-spool" color preservation. Two or three coats thinned slightly (10%) with water.

Liquitex or other brand name gloss medium sold in art supply stores. Water-based product that works wonders. It's also cheap.

I did a couple test wraps today using garnet and rust Gudebrod, then sprayed it with Krylon Crystal Clear, let it dry about an hour and then put on a coat of Flex Coat Lite and a coat of Perma Gloss on the other. No color change, in fact the color is somewhat brighter than on the spool. The only problem I can see in using it is that a person would have to mask the rod to avoid any overspray on the blank. I use the spray on inscriptions and that works great

Anyone else ever tried it?

Yes, Bob
I use spray laquers for inscriptions, too

Pavel,
Moscow, RU