Painting
Haha yea I am committed to this. As far as paints I used:
Golden Fluid Acrylics
Golden or Liquidtex Heavy Body Artist Acrylics
Speed Ball Black and White Caligraphy Ink
Pledge Multi-Surface Acrylic Sealer (yes pledge lol, a couple drops can make your washes really fill in the tiny crevices)
Distilled water for dilution purposes
Hy-Tech Shield's All #50 Non-Toxic Sealant
I had actually never painted before this so I spent a few weeks scouring the internet for tutorials. As you said with the vivarium scene it is almost all "natural debris" but I wanted a cliff face instead of a tree/above ground root system. Most of my construction techniques came from
Lizard Landscapes. That guy makes some great how-to videos on YouTube (as long as you can tolerate the random OMG I love Christianity interludes haha). If you want to know how to sculpt styrofoam and use Foam Coat/mortar he is your guy. His painting style on the other hand focused a bit too much on stippling so I found some awesome tutorials from the model train groups and the role-playing, miniature army, board game guys.
I bought a cheap air brush from Walmart back in their "air tools" section. As long as you have a decent air compressor it works fine even though they say you need a much larger one. Just spray in bursts so it has time to refill.
I made a batch of dark grey paint using I believe the heavy body white and mars black fluid. Always add dark to the light, you'll save paint that way. Once you find color you like make a **** ton of it. Since it is your base coat you will mess up down the line and it is a ***** having to try and match colors again from scratch lol. For the air gun just slowly dilute it distilled water until it feels right to go through the air gun. My consistency was pretty close to about 2% milk. An acrylic thinning medium would have been better to use as it contains the bonding agents but Michael's was out both times I actually remembered to try and buy some. Seeing some of the bonding issues I am having I would have to recommend it is worth it. It is kind of expensive and hard to find so I would still be sparing with it.
I would put down a coat one piece at a time. Once I made it through all of the pieces I went back with another light coat. The next day, about at the same time, I flipped it over and got the other side the same double spray way. Next day I would come back and hit all of the misc spots.
After everything dried for a day or two I threw on a quick black wash. This allows you to add some shading to all of the crevices while keeping the main surface area the same color. This first mix was rather thin at a ratio of about 2 drop calligraphy ink, 2 drop Pledge Multi-Surface; and 25-30 drops of distilled water. If you can find some 1 ml syringes it actually makes measuring quite easy as each syringe holds right around 25 drops. I mixed everything in a red solo cup and used a 2" sponge brush to apply the wash. Just fill up the brush and dab it on the surface until you have thoroughly coated the entire piece. It you have any major pooling areas you can roll up the tip of a paper towel and dry the crevices out. Remember you are trying to only shade the crevices so the more there is the better that will work, just don't let the water start dissolving old paint. Afterwards, let it dry for a couple days. If it still isn't dark enough don't do anything yet. You can darken it up slightly in between drybrush layers and the main shading wash actually doesn't take place until the end so there is plenty of time. Plus quick, in succession washes can damage the texture of your model.
Once dry you can release your army of dry brush coats lol. Really you can get away with just one coat of white but it is much more fun to add some depth. In the end I did roughly three shades of dry brushing, making sure to use considerably less paint with each lighter coat. Dry brushing allows you to only hit the upper surfaces of your model. The more paint you load on the brush or the harder/higher number of strokes in one area increase the amount of color you let down. So for the first coat dry the majority of the paint off on a paper towel (to the point that maybe 15% is left on the brush) and start randomly painting. If you have never done it before TEST FIRST! The purpose of this is to just barely get the surface, you will leave more paint the first few times you do it and let out an "Oh ****!" haha. Try and get the majority of the rock face and let dry. Come back around with a lighter shade and do the exact same thing but with less paint and less force. You can do this as many times as you want getting lighter and lighter. On your last coat use pure white and really dry that brush out. Be a bit more meticulous with your strokes and try to highlight only major protuberances.
If you want to add any color to your model the drybrushing stage is where to do it. I added some iron/rust colored layers in my cliff just so I wasn't completely grey-scale. Try to keep your layers synchronized so you aren't unnecessarily covering up previous work. Just a heads up, a "rust" color can be obtained using red (pyrrole), yellow (hansa), and black (carbon). Start with yellow, add red until you get a decent orange, then slowly add black to bring the color down to a bright brown rust color. It makes life easier using named pigments since you will always get the same results (generic colors simply called "red" can vary significantly in the types and concentrations of the pigments used). Plus you will get to sound like Bob Ross and that's just freaking awesome.
Another quick tip, using washes on the "rust" sections helps tremendously. Use roughly the same color as before, maybe a little less black, and dilute it to a ratio of about 1:10 or 1:15 (color:water, you can add pledge too if you only want to focus on crevices). After your last coat is dry, put some paper towels around the rust zone (so you only stain that area and you don't have long brown streaks down your model) and put a few dabs on with the sponge brush. The wash allows everything to blend together and keeps spots from looking out of place. Feel free to add more paint afterwards and wash again anytime something is too jarring or too dulled. Remember to ask other people how it looks as well. You can very easily get caught in paint/repaint loop if you are not careful.
Simple black washes can be used over the entire model if things start becoming too light. Just try not to be overzealous with them since there is a couple day wait time. Also remember you can always add color but you can't take it away. The wash cannot save you if you want to lighten things up.
Once you are happy with the color it is time to do the final shading black wash. For this you actually make a 1:1 mixture of Elmer's Glue All Multi-Purpose Glue and distilled water. Evenly spray across the face of your model and let dry for a day. Once dry, use the 1:1:15 black wash mix and do the same as the first black wash. The sealant coat helps to keep it off the upper surfaces even more while still allowing it to soak into the crevices. If you need darker add more pigment, but a 1:1:10-1:1:15 should get you pretty well. This is the video that gave me that idea:
For the final sealant I used the Hy-Tech Shields-All #50. I feel this is the portion I am the most weary of. The sealant is actually quite good. It is one of the only non-toxic ones you can find out there and it is super easy to spray with just a basic spray bottle. On the other hand this is the last layer before I started siliconing so it might also be the culprit that screwed me. That aside, I did basically the exact same procedure as the original base coats of paint but without the same day second light coat. Hit one side, go to next piece, repeat. Next day flip over and do the other side. I let it sit a couple days to finish curing before I started siliconing. One big piece of advice, take a couple pots or whatever you can find to set the model up on. As the sealant runs off the side of the model it will adhere to whatever it touches. So if you leave your model on the table it will seal itself to the table as well. At least with the pots you can create a drip edge so that any excess sealant simply falls off. I think I put on three coats all together.
As far as silicone goes, well I basically described that in my other posts but I can go into more detail if anyone wants. I will mention I only siliconed the parts of the rockface that would fully come into contact with water (i.e. submerged parts, areas near the pots, etc.). The Shields-All is designed to work in 99% humidity, just not to be submerged in water. I also siliconed most of the backs and sides just to add a little protection when I assembled and disassembled the waterfall. This actually proved to be quite fortuitous as I really could have messed up my heavily painted areas if I had siliconed them and they took on water.
Hopefully this helps other people out. I meant to write a bunch of primers on all of this stuff as I was doing it but was always too lazy. At least these after the fact tutorials are better than nothing