Lidstrom Lab French Press

French Press

Collect your equipment:

• 1- Cell cylinder
• 2- Screw valve
• 3- Piston
• 4- Cylinder cap
• 5- Spigot

Prepare the equipment:

• Check the condition of the O-rings on the piston and cylinder bottom before starting your extraction

- If they are shredded, sticky or warped you should change them

- There are 2 types of O-ring, flat and rounded; the rounded O-ring should be positioned on the outside

• Check the condition of the nylon ball housed in the screw valve

- The ball must be rounded to effectively adjust pressure

- Flattened or squared off balls should be changed out

- Use a razor blade to pry the malformed ball out of the housing and place a new ball in the opening

• Refridgerate setup at 4°C until thoroughly cold

You must have someone show you how to operate the press itself if you have never used it, but here is an overview of the press controls:

• 1- Pressure gauge
• 2- Pressure dial (increase/decrease psi)
• 3- Ratio selector (up/down)
• 4- Platform/riser (for micro cells)
• 5- Guide plate (swings to secure the fully withdrawn piston)

Turn on the machine and set working pressure:

• Toggle machine on
• Use the pressure dial to increase to a MAX of 1000 psi (for micro cell cylinders)

Prepare your sample:

• Invert the assembled cylinder, remove the cap, and pull the piston back until you see the grooves indicating max volume

• Load up to ~3 ml of sample into the core of the cylinder
• Make sure the screw valve is slightly open (otherwise the air trapped in the core will not have a release and you will have a hard time getting the cap to seat properly)
• Fit the cap onto the cylinder, making sure the O-rings are snug inside the core

- Here is where you run the risk of losing sample, either out the spigot (if you force the cap on too hard and the valve isn't cracked), or out of the core (if you overfilled it); go slow!

• If you put fewer than 3 mls of sample in the core, you can depress the piston a little bit (you will get a feel for this as you use the press more)
• As gracefully as you can, flip the fully assembled cylinder, with piston pulled back, into the upright position
• Tighten the screw valve, but only "finger tight"!

- DO NOT wrench it closed -- over-tightening will cause your nylon ball to flatten or shear, and can result in annoying repairs to remove pieces stuck in the cylinder outlets

- While the press is in operation, you are going to manually adjust the pressure inside the cylinder using this valve, and it's a very gentle adjustment...turns will only be a fraction of an inch to increase or decrease pressure!

Put the cylinder onto the platform:

• Swing the guide plate into place
• Adjust the cylinder orientation so that you can operate the screw valve and also collect the sample as it exits the spigot
• Be especially careful that the arms on the top of the piston will not be crushed by the screws protruding from the guide plate!

Start the press:

• Check to make sure the pressure gauge indicates 1000 psi
• Using a bit of muscle, pull the ratio selector level from "down" to "medium" position

(I think if you don't have the riser you would select "high", but I never have)

• The press is going to slooooowwwwllllly elevate the platform upwards, AND IT SEEMS WAY TOO FAST THE FIRST TIME IT HAPPENS, but I promise you have time to pick up your collection tube in your right hand, and poise your pressure-adjusting left hand on the screw valve

- It's a good time to double check that your valve is closed (but not too tightly!)!!

- Valve twisted towards you tightens and increases pressure

- The valve twisted away from you loosens and decreases the pressure