You choose your color combination carefully, so prevent surprises. This water-based compound locks in the original color and luster of your thread, so you can enjoy the thread colors you selected without undesired changes. It applies easily with a small brush and is compatible with any finish. Available: 1 oz., 4 oz.
I used scarlet thread for new guides on an old rod remake. Was worried the thread color would darken or change after applying thread varnish so I got this. Followed instructions on the bottle applying two coats and allowed to dry the recommended time before coating with varnish. The color just pops through the varnish. Brush cleanup with water was easy. Highly recommend this U-40 color lock
I used the U-40 on some bright red and gold thread and both maintained their colors after several coats of finish. It went on very easy straight from the bottle and didn't have any bubbles or thick spots. Great product.