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Separate Sand and Water in Glass Vase Answered

I'd like to hear some suggestions for separating sand and water in a 4" diameter glass vase. I'm doing an arduino project that involves having a dyed deep blue mineral oil as a non-evaporating "water" atop about 4 inches of sand in a glass vase. I experimented with drizzling Loctite epoxy and it leaked about 1/4" into the sand, so it wasn't very elegant (created a layered look - dry sand, wet sand, epoxy, water). I'd like the delineation to be as clean, but easily implemented, as possible.

Worst case scenario is that I wrap something around the vase to hide the transition, but I'd like to avoid that if possible. 

I suppose another option is to stack 2 separate glass vessels, but im struggling with thinking of a good way to do that too...

Perhaps this is also a non-issue...I should see if the deep blue mineral oil is even visible if put directly INTO the sand.

Thanks in advance.


As said, fixing the sand one way or the other is your goal here.
Problem is that you say you need the sand to be dry, a wet fix with wax, resin or just paint would be far easier to do.
To keep the dry look you need to impregnate the sand with something that repells your oil good enough to prevent it from soaking in - not easy with gravity around...
Silicone and most weather sprays will mix or dissolve in most oils.

Might not work as expected, so do a small scale test first:
Dissolve some ABS plastic in Acetone, like half a shotglss full of acetone and keep adding small pieces of ABS until the mix becomes like honey in the texture.
Clear or translucent ABS is best but any will do for trying it out.
You now have "plastic glue" that is far too thick for the purpose but should have enough plastic dissolved to fix your sand in place once you dilute it with more acetone.
Take an amount that is sufficient to wet your sand sample with it and make sure it is enough to make your glue mix really liquid again.
I prefer to use a sheet of baking paper for the mixing and wetting but use whatever you have at hand.
Once the sand is wet with mix put in your desired container and start to compact it with a dowel or similar, making sure the surface has the look you desire.
Let dry until you no longer smell any acetone, then warm it up to check if really no acetone vapor escapes anymore.
Once really dry add your oil and it should stay without going into the sand or disturbing the sand.

waterproof the sand.

I like it - have a good product suggestion? Like a simple shoe spray?

sounds like a good start. Maybe camp dry. For jackets, tents, etc.

whoops... reading for content... try wetting the sand. Mineral oil shouldn't mix. Maybe.

try using gel wax instead of mineral oil