Venger's Flasking Pictorial
Below you'll find a pictorial of the flasking process. We've
tried to make it logical without overdoing the graphics
or being preachy about it. Hope it's useful :)
NEW! Venger's own flasking kit!
Part I - Preparation
Prep Materials (May be altered for your own use):
16 oz clear canning jars w/screw type lids.
Volumetric measuring flasks
Aluminum foil, cut into 5x5" squares
A work in progress
Flasking preparation is a relatively easy series of steps requiring
good attention to detail. Cleanliness is required but sterility is not
needed at this point.
These are Nalgene volumetric flasks, used for measuring water
to a reasonable accuracy. These particular flasks are accurate
to within .60ml, except the 250ml, accurate to .30ml
From left to right, 250, 500 and 1000ml flasks. The different
sizes allow me to accurately measure the amount of distilled
water I need in 250ml increments.
This is an Ohaus digital scale, accurate to .10grams
The scale is tared to account for the weight of the
container that holds what you're actually weighing.
That means you first place an empty container on the scale
and press the button which stores the weight and then zeros
the scale, assuring that the weight you see on the readout
is only for the media you're weighing out.
I usually make 750ml of media at a time. Using the Nalgene
volumetric flasks, I fill the 500 and the 250ml to the appropriate
level on each. I then turn on the scale, tare my container
(10.6gms) and wait for the scale to re-zero. The media I use
calls for 34gms of media per liter (1000ml).
Multiplying 34 x .75 gives me the amount of media I need
for my 750ml of water, in this case, 25.5gm.
The distilled water is placed into the aluminum pan and heated.
I let the water get to about 150 degrees before I add the media.
After adding, stir constantly until the mixture is just below the
boiling point. Keep there for just a few minutes, usually until the
mixture starts to clear. You can then equally divide the media
between however many flasks you're going to cook. I place about
125ml of media in each jar. Better to have too much than too little.
After pouring the media, you can close up your jars. You'll note
a piece of cotton in the lid. I punch a 3/8" hole in each lid and
stuff a piece of cotton ball thru the hole. Note: Punching a hole
is better than drilling. Punching leaves "teeth" on the inside of
the lid, something for the cotton to grab. Drilling won't. I then add
a drop or two of Copper compound to the part of the cotton ball that
is on the inside of the lid. Copper, being a natural fungicide, helps
to keep the flasks contaminant free. Doesn't always work, but
every little bit helps. The copper source we use is "Knox-Ich",
a preparation normally used in fresh water aquariums. Don't
tighten the lids down all the way at this point. Just barely touch
down and then back off a little. Place a 5x5" square of aluminum
foil over the top of each jar and smooth down.
The flasks are then loaded into your cooker with an appropriate
amount of distilled water, closed up and sealed according to the
directions for your particular cooker. We cook the flasks at 18psi
for 20 minutes. Others have their own favorite pressure and time,
but 17psi and 20 minutes is about the minimum. Bear in mind here
that the time does not start until you've reached your final pressure!
After cooking the flasks for 20 minutes at 18psi, we let the cooker
sit without disturbance until the guage reads zero. There IS still
pressure in there, but it's probably not lethal. We then move the
cooker into the hood and allow it to cool, sometimes for a few hours,
sometimes all night. That depends on what time it is and if we're
planning on using the flasks today, tomorrow or next week. Once
the cooker has been opened, you can flask as soon as the media
has gelled and cooled.
Fair warning! Until you open or purposely vent the cooker, the
contents are sterile. If opened inside the hood, the contents will
remain sterile, inside and out. Removing the flasks from the hood
or from the cooker into room air will contaminate the outside of the
Part II - Seed sowing - This is a sterile procedure!
Materials we use:
Sterile flasks with media, prepared as above
1/2 ml specimen tubes
5% bleach solution (20 parts distilled water, 1 part bleach)
1/2 teaspoon dish soap, added to above water
sterile distilled water
2 sterile eye droppers
2 bleach sterilized towels
1 2qt rubbermaid container
1 small plate
Below is a pic of our loaded hood. The hood is first UV sterilized
for 30 minutes with the cover on. The UV is then shut off and the
motor started. The cover is removed and the filter is allowed to
run for 10 minutes or so. The entire inside is then wiped down with
a towel presoaked in a 5% bleach and water solution. Cleaning
starts close to the filter and ends at the outside end of the work
area. The hood is then loaded with sterile items. Items that are not
sterile going in are sterilized at the edge of the airstream before
being placed further in the work area. Starting at the bottom left
and going clockwise, a rubbermaid container with the bleach
solution. In it are gloves and a wiping towel. Then a plate with a
pile of sterile 1/2ml tubes, a jar of bleach solution with a sterile
eyedropper, the flasks, a jar of sterile water (Sterilized with the
flasks and media), sterile Q-tips, and finally a sterile towel with
scissors and forceps.
Photo 2 & 3.
In the two photos below, I've placed some Orchid seed (about the
volume of a piece of rice) in a sterile 1/2ml tube and am adding
bleach solution to the tube to sterilize the seed. Leave an air
bubble at the top of the tube. I agitate the tube gently for 30
seconds out of every 60, repeating until 4 minutes have passed.
I allow the seed to settle for the final minute.
In this photo, I'm using a Q-tip to draw off water from the tube,
removing as much as possible. I then refill the tube with sterile
water, agitate gently, wait for the seed to settle again, and then
draw off the water. Repeat the sterile water process and then
fill the tube one final time. You'll need 6 Q-tips to complete this
After filling the tube and gently agitating, carefully open the flask
and pour the seed and water into the flask. Shaking the tube to
dislodge seed and water at the bottom is ok, but do not tap the
tube on the flask. When finished, set the tube aside, carefully
put the lid on the flask, tighten well, place the foil back over
the top of the flask and smooth down.
The finished product! Label your flask with a stick on label or
use a wax pencil. Make sure that you keep detailed records!
More to come!