Every mad scientist needs gruesome specimens and demented experiments on display. Whether actually experimenting with reanimation or just keeping a extra brain on hand for a rainy day, the brain is a classic specimen!

This one is on life support, with blinking LEDs indicating brain activity. What is he plotting in there, and just what does he really think he can do from inside the jar? Mine is called Donovan.

Step 1: Vision and Materials

The first thing one needs to know is what the end product should look like. I decided I wanted a brain on wires, with blinking lights indicating activity. The brain should be floating in liquid, ideally bubbling liquid, in a jar that looked vaguely Frankensteinian/steampunk.

I ended up using:
A big plastic pretzel jar from CostCo
Plastic wall anchors
A hubcap from a Chevy
Two 99Cent Only Store "light swords"
Wires from an old TV
A fish aquarium aerator with tubing and a pump
Great Stuff
Hot glue
Masking tape, Krylon spray paints, various acrylic paints, sandpaper.
Screwdriver, soldering iron, dremel

Step 2: The Jar

I decided to begin with the bottle itself. A brain without a home is a sad sight indeed.
I followed a similar method to my Mad Scientist's Display Cases .

After my football watching, snack food scarfing friends emptied an industrial sized jar of pretzels from CostCo, I had my jar!
I began by cleaning it off and masking everything I wanted to leave clear. There were "bands" already molded into the plastic, so I decided those should become metallic. As with other jars I have made, I covered the bottom so I could light it from underneath later.

After masking, I lightly sanded the uncovered plastic with fine grit sandpaper. Since I use Krylon Fusion as a primer, this is not really necessary, but I think it helps the paint stick better.

I applied a coat of black satin Krylon Fusion as a base. Once dry, I Painted over the black with a thin coat of silver metallic, and then "dusted" with a very thin coat of a gold/coppery color I had. This gave it a thematic / chromatic similarity to my other jars, but still maintained a unique silvery color.

Step 3: Detailing the Jar

The real difference between a creepy specimen jar and a recycled pretzel jar is the detail work.

I wanted something that really said industrial, hacked, repurposed, and slightly mad. My first details were the conductors / insulators around the top ring of the jar. I know - conductors and insulators are opposites, so which are they, right? It depends on when you ask. They are whichever I think sounds cooler in that particular moment. ;-)

I thought the wall anchors used to hand heavy objects in drywall had potential there. I got two sizes - green and gray - and decided I'd alternate them for visual interest.

This time I had to put them on little sticks to paint. I used an off-white Krylon Fusion as a primer to suggest ceramic. I was thinking insulator at that moment.

So, once dry, I just hot glued them into place around the edge of the jar. Realistically, it may be better to hot glue them in place first, and then paint the jar, but I have not had significant issues with doing it in this order, and it is much easier.

Step 4: Details Part 2 - Hot Glue!

Now that I used the hot glue for the insulators, I can cast other details. I used simple sand casting, as I intended only to put round bolts/rivets/whatever around the perimeter of the jar. Sandcasting with hot glue can make a nice cast iron look, especially if what you want is a somewhat rough, pitted look.

I filled a little container with the finest sand I could find in my backyard. I added a little water, and it was ready to take an impression.

I used a CO2 cartridge from a BB gun to make the impression. I simply pressed it into the sand as deep as I wanted the final cast to be.

I did have to "touch up" the impressions as I went, since the sand would deform some of the earlier impressions as new ones were made.

Once I made the impressions, it was simple enough to fill them with hot glue and wait for them to cool. When they looked cool enough, I used the sticks from the previous step to poke the tacky glue and lift the casts out. Dipping them in cold water would harden them more if necessary.

There is a lot of sand stuck to them. I just rubbed/washed that off and dried them before painting.

Step 5: Painting and Applying the Hot Glue Castings

Painting hot glue is pretty straightforward. I just painted them black with regular black Krylon spray paint from Wal-Mart, then applied 2 metallic colors. I started with a copper first, then applied silver on top. Again, chromatically similar to the paint already on the jar, but not attempting to be identical.

Once dry, I simply hot glued the new details to the jar where I wanted them.

Step 6: The Interface

So a jar holding a living brain is going to need more than a little plastic snap on lid. It needs something that suggests technology, power, maybe a little madness. Providence and Chevrolet provided just the thing.

There I am, coming home on the freeway, when what should I see on the shoulder but a little Chevy hubcap. As it gleamed in the sun, I knew it was exactly what I needed. No one was behind me, so... Slow down, pull over, open the door, snap! It's in the car and I'm on my way home to paint!

As it turns out, the thing fit on the jar like it was engineered precisely for that purpose. There are little plastic pieces that snap right over the rim of the jar and hold it so tightly that I can lift the whole thing - brain and water included - simply by lifting the hubcap. Sweet, right?

I decided that the Chevy logo was not going to work for my theme, so I treated it the same as the jar - taped up what I did not want to paint and sanded the rest - with two differences.

First, it turns out the people at Chevy use a really high quality plastic or resin to cover their logo. It is clear, hard, and REALLY tough to scratch. I had to use coarse sandpaper to start, only gradually using finer and fined sheets. It took WAAYYY more time and effort than the pretzel jar.

Second, though I did not really want to repaint the silver of the hubcap, I did nothing to cover that part. I let the overspray happen.

Once the logo was covered in black, I added a coat of silver and a lighter coat of copper. I also added a light dusting of copper to the silver of the hubcap itself.

If I was really good at planning and soldering, I probably would have matched up the jar details with the 6 "bolts" on the cap, and I would have drilled a hole in at least one of the hollow bolts to run wires through. I didn't think about the detail thing until later, and as for running the wires through, I decided it would make it too tough for me to finish the brain and when done, the brain and lid would be permanently combined.

Step 7: Finishing the Jar

I like little details on my props that make them interesting even under full daylight. For this jar, I mixed up some red acrylic and water for an "oxidation" that would run down the jar. I also added this to the conductors / insulators. Only after adding this did I remove the paper covering the "glass".

I also added some small splashes of green and a particularly nasty splotch of green, where some horrible stuff got on the jar and the doctor, in his mania, never bothered to clean up.

On the inside, I flicked some red paint from my brush on the inside of the walls. There has to be blood involved somewhere, right?

Step 8: The LEDs.

I knew I wanted flashing LEDs, and I also knew I did not want to spend a lot of time or money building some kind of apparatus for that. So I went to my local 99 Cents Only and got a couple of the flashing light swords.

It was a pretty simple matter to open them up, solder extension wires in, and screw them back together.

Once they were long enough, I taped them into place inside my brain mold. It's supposed to be for making gelatin brains, but I figured Great Stuff expanding foam would work too.

Step 9: The Brain!

Once the LEDs were more or less where I expected them to end up, it was time to make the brain itself. For this I chose Great Stuff expanding foam insulation.

This is really a great material for something like this. It seems to dry waterproof and light, and can be carved when dry too. There are some things one should know about it before making a brain in a jello-mold with it though.

First, it expands as it cures, and it apparently cures from the outside first. I'm guessing from contact with the air. Because of this, large molds should be done in thin layers and allowed to cure. I did NOT do this. I simply filled it up with Great Stuff and waited for it to dry. In a few hours, the top had dried and expanded. In the process, it lifted away from the bottom and could not be pressed back down. The bottom (Which was the top of the brain) never did cure. It was a mess! I had a base that puffed up way too much, and no top. The LEDs were awash in a nasty sticky soup of uncured foam.

I pulled them out and cleaned them. I also cleaned out the mold with boiling water followed by Goof Off and more boiling water. It does interesting things in contact with boiling water. Anyway...

I flipped the cured 1/2 over and kind of hand-molded my brain. The LED patterns I worried so much about were right out the window, and I just did my best not to clump them all together. Finally it cured.

If I were using this method again, I would remember to apply the great stuff in thin layers. Also, I would use only 1/2 of the brain mold. Using the whole thing made it too big and it sat too high in the water.

If you are wondering, I did put a thin layer of vegetable oil on the mold as a release agent. Based on how the stuff cured though, and from the smoothness of the mold, I think that was probably unnecessary.

Now it was time to paint.

Step 10: The Technicolor Brain

Brains are gray right? Well, only dead ones are gray. Live brains are pinkish. This brain is somewhere in between.

I have a long history with SFX makeup, and I tend to think in terms of making a prop realistic under full light. I only started doing "stage makeup" this year, and painting props is new to me altogether. It didn't take long for me to understand why so many Halloween props are painted in garish, almost childish paint jobs. Subtleties are lost in low light situations like a haunt would have. So I sucked it up and painted my own high contrast brain using pink, red, and gray.

Normally, I work from darkest colors to brightest. This time, I wanted the "shadow" areas to be pink or red, with the outer surface more gray. Whether a brain really looks like that or not is irrelevant, I think. It's about people's expectations and about creating a response, right?

So, I liberally applied pink acrylic paint all over the recesses of the brain, thinning it a bit with water to get it in the crevices. Then I "highlighted" the edges in red. It's an organ. It has to have red in there. Finally, I coated all the high parts with gray paint.

The end result is a paint job as subtle as a circus poster, but under indoor lighting with the LEDs on, I think it works well.

Step 11: Water, Bubbles, and Getting It Right.

I wanted the brain floating in bubbles. Lots of bubbles. At the same store where I got the swords they had aquarium stuff. I picked up a "Bubble Bar" aerator and put that at the bottom, with tubing running to an aquarium air pump.

I cut a notch in the rim of the jar for the air hose and the wires to go through under the cap.

I decided all the sword handles needed was a paint job to fit right in, so I painted them the same combination of black and metallics as the rest of the cap and hot glued them into place - buttons up, of course.

The brain floated far too high in the water, so I added some lead weights from a local tire store to sink it a bit. If I had made only 1/2 the brain, this would not have been necessary at all.

The brain fit right into the mouth of the jar and floated about like I imagined it should. To mask the bubble bar, I originally added a bit of milk. I don't recommend that approach. Turns out clear water works just fine, without the smell.

I bought a light up LED coaster to light from the bottom, to disappointing result. No matter. The actual prop shelf will have much brighter light coming up from underneath.

Step 12: The Final Product

Here are a couple of videos of the brain and jar under different lighting conditions. Both are brighter than the actual haunt is likely to be, so you can more easily see details.