OK, I have begun a formal test, and so far, the only thing I have concluded is that I am impatient, LOL!
It's Monday morning, and I started preparing for this test about a week ago. I think you all realize I'm a plan, worry, plan some more, over-analyze, make tweaks, over-think some more, then set out to do someting... But this time, I tried my hardest to build a test that will actually prove or disprove... and if I disprove, I hope to gain sufficient knowledge to make one final tweak before doing this for real.
I made up a small reservoir using a piece of scrap foam. The reservoir is deep enough and a large enough area for a good test. I caulked it, then painted it the same color as the riverbed.
Here is the teat piece, all painted and ready for a test pour.
Part of the objective for the top-coat is to have it subdue the rather "loud" sky-blue hue. I'm after a murky look, so I decided that adding some raw umber to teh top coat might look really good, so I did the math to set a 1:32 mixture of dye.
For the top coat, I have landed on Acrylic Gloss Medium (Liquitex brand) from Hobby Lobby. The river is an average of 17.5" wide, and is 54" long. I want the pour to be 1/8" deep, so all in, I need 1/2 gallon, or 2 quarts.
Doing the math, I needed 4 ounces of top-coat for the test, in order for the test pour to also be 1/8" deep. In order to get a 1:32 mixture, I needed to add 3/8 teaspoon of dye into the 4 ounces of gloss medium.
Thsi picture below is right after I poured the test 4oz into the test reservoir. The white are must be some gloss medium that didn't get mixed well. At this point, the gloss medium is still a milky white. It comes a milky white, but once cured, it is clear. The raw umber dye, when mixed into the milky white medium takes on a slate gray appearance, that should clear up to a murky greenish blue tint when fully cured.
Here's a picture at 14 hours in, which I took Sunday. Atthis point, it was still very much a liquid. I could have poured most of it out at this point. You can see the slate color starting to give way to the raw umber here.
I wish I would have taken a poicture this morning, about 36 hours into it... It's now semi-cured... tacky to the touch, and the raw umber is still emerging as the milky white fades away.
I'll post more pics tonight, which will be closer to the 48 hour mark.