This is take two. Take one failed and I reckoned that it was because I was using ready-made ikea candles for the goo.
I started from scratch, using paraffin. As per retro's suggestions, I started with 1/3 perk, 2/3 paraffin, now I'm at something like 1/5 perk, 4/5 paraffin and my goo still won't float yet, even in pure antifreeze. This was the case on the first take (I had to use many more candles than retro was suggesting) and I thought that this was because of the candle quality/materials.
I'm currently testing using a test tube filled with antifreeze. As soon as I can get my goo to float in there, I'll adjust to the correct antifreeze/water ratios in order to get 1.03 goo density.
As retro suggests, I'm using a straw to get a sample of goo, slightly round it up using my fingers and drop it in the tube. I then have to turn the tube upside down a few times or the goo will float. Not that I don't want it to float, but it's floating due to other reasons that I'm guessing have to do with surface tension or bubbles stuck on it and not because it's less dense. After some stirring up, it always sinks to the bottom and I have to get back to the drawing board and get more paraffin in the goo.
Am I on the right track? Or will it end like the first take? Am I doing something wrong?