Making of the alchemists's cabinet

The bottles will be placed in a specially made cabinet, for which I chose to use papier maché, as it is light but very sturdy.
I learned a lot from my previous experiment to make a small bookcase from papier maché. I had the idea to reinforce the edge of the shelves with plastic u-shaped edges (from the DIY shop), and it worked great: the cardboard did not move, and the shelf edges remained straight during the whole building process and afterwards. However, I had not equiped the sides of the cardboard box (the vertical edges) in the same way, so when they got wet (a natural part of the process of putting papier maché on something), they got all wavy. This thime, I put plastic edges on every single edge (see picture left), and painted the carboard with acrylic prior to covering with paper strips to limit the water uptake.
The upper picture shows the almost complete cardboard base, with the edge reinforcements (glued with wood glue and masking tape). The only missing part is the top, which is a single flat cardboard piece cut to shape. I filled the corners with paper paste for strength.
The right side picture shows the cabinet covered with paper strips (the Canard Enchainé gives high quality, water resilient strips, as you can see).
I managed to get a satifactory finish for the paint, but it is still rather fragile. I am looking now for something watertight and resilient (and not too expensive) to finish it...