Ahh, it’s BigJohnny from ICMAG Forums, I was just going to suggest you come over here for help.
It could be your filtering procedures, but burned rubber smell is most likely too high a boiling rate, which is usually brought on by not getting the vacuum down low enough.
Are you still using the BVV stirrer/mantle? If so, I suggest bypassing the PID controller and feeding the mantle with a power regulator, be it a simple $40 Variac (10 amp) or any of the other options I came up with in my thread titled “Distillation controllers with both temperature and power control.”
You simply open up the base of the stirrer/mantle, disconnect the leads to the mantle, and connect a couple of wires leading to the outside where you can plug them into the Variac. Plug the Variac into a Kill-A-Watt power meter so you can monitor exactly what wattage produces what boiling rate.
A quote from a quote in my controller thread,
"Now on to the kind of controller like I said this is not about the best controller. It’s about what that controller needs to be able to do for you. The controller needs to be able to adjust the amount of heat being put into the boiler. In a steady variable amount you want the heat to be as steady as possible. You do not want it cycling on and off wildly. If cycle times are more than say one time a second. It’s more than likely not a good choice because every time it cycles on more vapors are created. Then when it cycles off no vapors are created and you get surging. It would be like if you were trying to use a hose and your kid was around the corner pinching off the hose and laughing at you because the hose sprays then shuts off, then sprays and shuts off again. This variance in vapor amounts can and will wreak havoc on the still operation causing surging which in turn will cause smearing of the heads hearts and tails and it can give you false readings on a thermometer in a reflux column.
The other thing you do not want is a controller that works off of temps. A thermostat controller or PID controller (without manual mode) are examples. First off we can’t control a still by boiler temp. As it will be ever changing and these types of controllers cycle very widely. They reach the set temp while at full power then shut off all power till the temp drops below the lower setting which is usually a long time span. Since it’s trying to control temps and you are trying to control amounts of vapor produced the temp settings usually get set high so you get really long surges of full power heat. All this creates bad surging within the still and the same holds true as stated above about the surging."
Another quote from a quote,
“I find a variac gives me the best temperature control and the most even heating, far above a PID which is above a dimmer. A guy from california is selling a good variac for 38$ shipped, I got his 46$ version (10amp).”
BTW, BigJohnny just posted this up at ICMAG Forums, maybe you guys could help him out over here,
"Bentonite clay, how to use it?
basic question, how do you use the clay to clarify distillate?
after winterizing and filtering out the waxes through 3 stages, do you just add clay into the ethanol/bho solution and mix under heat for a little while?
How much clay is added to the solution?"