I have started testing last week and am still in the process of determining which sand and liquid medium to use. I am doing these tests before I spend the time to build a frame. As anticipated, my constrains are very similar to the challenges I mentioned in the Design review. However, I am now aware of the details since I started testing.

Here are my top five constrains:

1. Sand: it is actually tricky to get sand that has the desired buoyancy and in the same time be light enough to be held by air bubbles. Also the sand needs to be fine enough to pass through very tight air bubbles. From my experiments so far very fine sand tends to make the water turbid and it also sticks together creating a huge particle.
2. Liquid Medium: I think this is the most challenging by far in the project. The fluid used in current Sand Pictures is a trade secret. I have been able to fix a sand picture frame with 50% water, 25% Alcohol and 25% salted water.
3. Sealing: Sealing a frame like this tough task. My design will have two thin glass panels sealed with epoxy. This operation is tricky because fluid and sand need to be added while the frame is being sealed.
4. Additions:  Adding another fluid medium like oil or ink will be tricky since it will disturb the motion of the sand. Also having a pressure pump might not be feasible because the sand might clog it after sometime.
5. Time: I will need to make to take more aggressive steps in building and testing with a frame after testing. I understand that this might require building a couple of frames discovering flaws and attempting to solve them in a timely manner.