Thanks for the info, I sourced better sorted material but it is still old from last October and was able to make some slightly lighter extract.
http://m.imgur.com/a/xNQbl
But it is still quite dark.
When you say extract at subzero, I keep my butane in a freezer until immediately before the extraction, is that good?
I have been running about 15 lbs of butane straight through the material.
The best result I was able to create was by leaving a vacuum and bringing the heat down to room temp and essentially freezing the muffin in place as shown in the first pic. Leaving bubbles in the extract.
I wanted to try propane butane mix but I'm u nsure if their are any other safety considerations. I am using a best value vac 5lb system.
http://www.bestvaluevacs.com/cls5lb-trs21-kit.html
The size of your base determines the pressure rating of your system. A 12" 13MPH high pressure clamp is rated at 150 psi at 70F and 100 psi at 250F.
For a certified blessed by the Pope installation, ASME says 6" and under is piping, which must meet 350psi for LPG, and over is a pressure vessel, which must meet 3X its maximum operating pressure.
Attached is a chart showing butane/propane mixes pressure at temperature.
We use butane/propane mixes up to 50/50, extracting at -50C or so, where it does two things. One is to keep the mixture thin enough to still push through the system with an auxiliary hot vapor tank, and the other is that as a C-3 sized molecule, it actually is more selective than the larger C-4 butane molecule when it comes to extracting the molecules larger than our C-21 targets, at those low temperatures.
Included in those larger about C-30 sized molecules, are chlorophyll, anthrocyanin plant pigments, and plant waxes, so it lightens our subzero extractions, rather than darkening them.
We keep our storage tank around 31F and use a counter flow heat exchanger at the point of injection to chill the LPG mixture, which saves trying to move a tank of jello through a skinny dip tube. We use liquid N2 on the coolant side, but CO2 could also be used, as could a -40C subzero chiller.
You can also use a 1/2" X 50' stainless coil in an alcohol dry ice bath, and just take it out of the bath when you aren't injecting, so the LPG doesn't get so thick it clogs the coil by the time you are ready to use it again.
We use 3/4" tank valves, to maximize flow at low temperatures.