PNat said:

c10h12n2o said:

WARNING: this is a little bit less than kosher, but i will provide the reasoning every guide says to let the PC zero out on its own. naturally the pressure falls once you kill the heat, and once it hits zero it goes below zero, then eventually back up. in my early work with agar, i had some contamination due to opening the PC when the pressure was negative, which led to sucking contams into my agar. what i like to do now is a little impatient, but i have not not seen any problems from it in the 15k to 20k plates i have done with this method. so here is what i like to do: i carefully watch the pressure as it falls, then right as it gets to zero, right before it crosses the line, i pop the vent. this means there is a small hiss of positive pressure being released from the valve (which is good, because it means nothing was sucked in), with less and less pressure as you get closer to zero, with negative pressure building if you wait too long (which sucks in contams). so right before zero, i put on protective gloves/mits, pop the valve, open the PC, and immediately tighten the lids on the media bottles and remove them

lids tightened and bottles removed from PC

c10

---

How do we do this with a PC that does not have a pressure gauge?

---

Hobbyist said:

PNat said:

c10h12n2o said:

WARNING: this is a little bit less than kosher, but i will provide the reasoning every guide says to let the PC zero out on its own. naturally the pressure falls once you kill the heat, and once it hits zero it goes below zero, then eventually back up. in my early work with agar, i had some contamination due to opening the PC when the pressure was negative, which led to sucking contams into my agar. what i like to do now is a little impatient, but i have not not seen any problems from it in the 15k to 20k plates i have done with this method. so here is what i like to do: i carefully watch the pressure as it falls, then right as it gets to zero, right before it crosses the line, i pop the vent. this means there is a small hiss of positive pressure being released from the valve (which is good, because it means nothing was sucked in), with less and less pressure as you get closer to zero, with negative pressure building if you wait too long (which sucks in contams). so right before zero, i put on protective gloves/mits, pop the valve, open the PC, and immediately tighten the lids on the media bottles and remove them

lids tightened and bottles removed from PC

c10

---

How do we do this with a PC that does not have a pressure gauge?

---

Just an idea..  You could time how long it takes for your pressure cooker to go from your usual sterilization pressure(15,16,17, etc) to 0 by starting your timer when you remove it from the heat and then stopping it when you hear the seal fall(the seal is officially called an Air Vent Cover Lock). 

Then in the future you can just walk into the kitchen and 2 minutes before it's due to fall and then remove the weight when it does.

Frankly though, simply listening for the seal to fall and immediately going to remove the weight is probably sufficient.

---

Grumio said:

Any input on these PE plates?

Started from a swab.

Only 1 plate showed any growth so transferred to 3 plates then took 3 samples from the best two plates and below is the result.

Are these good for grain now or should I transfer some more?

Plate 1:


Plate 2:


Plate 3:


Thanks

---

Hobbyist said:

PNat said:

How do we do this with a PC that does not have a pressure gauge?

---

Just an idea..  You could time how long it takes for your pressure cooker to go from your usual sterilization pressure(15,16,17, etc) to 0 by starting your timer when you remove it from the heat and then stopping it when you hear the seal fall(the seal is officially called an Air Vent Cover Lock). 

Then in the future you can just walk into the kitchen and 2 minutes before it's due to fall and then remove the weight when it does.

Frankly though, simply listening for the seal to fall and immediately going to remove the weight is probably sufficient.

---

HoneyBadger9321 said:

When I put my agar mixture into the microwave to disolve it down, it just gels up the agar and everything else is liquidy. So i cant really filter it. Am I not boiling/microwaving it enough? I do around 10min all together.

---

MrBovineJoni said:

HoneyBadger9321 said:

When I put my agar mixture into the microwave to disolve it down, it just gels up the agar and everything else is liquidy. So i cant really filter it. Am I not boiling/microwaving it enough? I do around 10min all together.

---

I'm not entirely sure I understood your question but basically when microwaving you need to almost bring it back to boil (with some mixing,shaking in the middle to ensure consistent heating).  It does not warm up evenly so you have to shake/mix it a few times (lid closed).

Agar has to reach >85C before solid chunks start to melt and due to how microwave oven works it never is 100% even. Then at around 32-38 it starts setting again so you have a window between 60C(too hot to handle for most people, also you get more condensation but other than visibility  that it is fine to have it) and 35C to pour it.

For my 1L media bottle (about 800ml of agar in there) I do about 6min x 600W, shake,  followed by 3 min at 600W and then I repeat it in 30s-60s chunks until all chunks have melted and the liquid is uniform. I find that using maximum power (900W in my case) produces too localised heat in places where waves end up concentrating more so it can almost burn by accident.

---

HoneyBadger9321 said:

The microwaving takes up a lot of the work time. Is it possible to just skip this step. The microwaving is to achive crystal clear agar, correct?

---

HoneyBadger9321 said:

Right yes! I was referring to the first (before PC-ing). I just cant seem to dissolve it completely and chunks still remain when i filter it. Maybe i am not doing it long enough. I had a look at RRs agar videos and there he does not cook it before PC-ing. Takes a lot of time for me and seems that the results are the same, just a little bit cloudy agar. I might be wrong tho?

---

HoneyBadger9321 said:

When I put my agar mixture into the microwave to disolve it down, it just gels up the agar and everything else is liquidy. So i cant really filter it. Am I not boiling/microwaving it enough? I do around 10min all together.

---