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plutoniusspasticus
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Petri dishes keep contaminating
#26886204 - 08/18/20 07:27 AM (3 years, 5 months ago) |
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I'm trying improve my sterile technique so I made 20 agar plates. I checked them 5 days later and they all have tiny white blobs on them. I used a sab, misted it with soapy water, used slow movements, minimized exposure time when opening the petris, didn't let my hands go over the petri dish. I pced the agar for 45 minutes and let it cool for 2 hours. I took a shower before. I used plenty of iso to clean everything. I used gloves and regularly cleaned them with iso. I work in a small room without air movement.
Here's a picture of one:

I don't know where the contam is coming from. Any advice would be great.
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LadysKnight
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I used to get those when I misted my sab.
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PrincessRosalina
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Re: Petri dishes keep contaminating [Re: LadysKnight]
#26886389 - 08/18/20 10:00 AM (3 years, 5 months ago) |
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Quote:
LadysKnight said: I used to get those when I misted my sab.
Do you just not mist anymore?
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LadysKnight
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Correct.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: LadysKnight]
#26886415 - 08/18/20 10:18 AM (3 years, 5 months ago) |
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It seems strange that spraying would be the problem. I'll try not spraying anyway.
Any other ideas anyone?
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maxmush
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Hmmm. Are those specks growing at all?
-------------------- Disclaimer: all information presented is intended for educational purposes only. All photos are only representations and not directly from the user.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: maxmush]
#26886476 - 08/18/20 10:41 AM (3 years, 5 months ago) |
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I've only just seen them so I don't know yet tbh. Up-close they look like white droplets.
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A.k.a
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It does look like bacteria but it might just be sediment it’s hard to say for sure without seeing them in person. Are they in the agar or on the surface?
Have you opened them since you made them or did you just pour them and wrap them?
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tryptkaloids
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Re: Petri dishes keep contaminating [Re: A.k.a]
#26886717 - 08/18/20 12:55 PM (3 years, 5 months ago) |
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Don't blame misting entirely. Blame overmisting. You dont need to soak the top
-------------------- "Remember, kids, the difference between science and screwing around is writing it down" -adam savage Flowchart for Recommended plan of action. Learn the tried and true way to grow mushrooms Use the Damn search engine After you know what you're doing, take a break Pick a book, Make some chips! Josex said:Don't take the site seriously bro, ain't worth it.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: A.k.a]
#26886738 - 08/18/20 01:05 PM (3 years, 5 months ago) |
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@A.k.a They're on the surface. I just poured them and wrapped them, haven't opened them.
Edited by plutoniusspasticus (08/18/20 01:09 PM)
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26886742 - 08/18/20 01:07 PM (3 years, 5 months ago) |
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@Onlinetryptkaloids I used a fine mister and I remember doing 3 sprays. Maybe it's still too much though.
Edited by plutoniusspasticus (08/18/20 01:08 PM)
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tryptkaloids
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Did you wipe your agar vessel before you poured?
-------------------- "Remember, kids, the difference between science and screwing around is writing it down" -adam savage Flowchart for Recommended plan of action. Learn the tried and true way to grow mushrooms Use the Damn search engine After you know what you're doing, take a break Pick a book, Make some chips! Josex said:Don't take the site seriously bro, ain't worth it.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26888084 - 08/19/20 09:58 AM (3 years, 5 months ago) |
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Yep, I cleaned the petri sleeve and the agar bottle with iso when I put them in the sab.
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tryptkaloids
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What was your media? Sterilization times? Did you remember to vent your PC.
-------------------- "Remember, kids, the difference between science and screwing around is writing it down" -adam savage Flowchart for Recommended plan of action. Learn the tried and true way to grow mushrooms Use the Damn search engine After you know what you're doing, take a break Pick a book, Make some chips! Josex said:Don't take the site seriously bro, ain't worth it.
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Spore211215
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26888495 - 08/19/20 02:04 PM (3 years, 5 months ago) |
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Could be what you’re misting with has contams hiding inside it. Are you using Iso, soapy water, or both? Maybe if the water is old it could be bringing stuff in you don’t want. I used to have a lot of problems with that but I tuned in my misting and hand movements and now I only get contams when I’m being careless
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tryptkaloids
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Re: Petri dishes keep contaminating [Re: Spore211215]
#26888537 - 08/19/20 02:22 PM (3 years, 5 months ago) |
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Could also be you were bumping the box. Did you rest your arms on the holes?
-------------------- "Remember, kids, the difference between science and screwing around is writing it down" -adam savage Flowchart for Recommended plan of action. Learn the tried and true way to grow mushrooms Use the Damn search engine After you know what you're doing, take a break Pick a book, Make some chips! Josex said:Don't take the site seriously bro, ain't worth it.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26888780 - 08/19/20 04:35 PM (3 years, 5 months ago) |
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I used lme. 45 minutes pced then I leave it in there for 2 hours to cool down. I used to instantly open once the pressure valve went down- that caused a lot of contamination.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: Spore211215]
#26888794 - 08/19/20 04:37 PM (3 years, 5 months ago) |
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I use a new batch of purified water and soap for each session. I didn't wait long for the mist to settle though. I saw a post from bod or RR and they said to work immediately. I wipe the sab and whatever I'm working with before I start. Perhaps I'm a little rough sometimes with my movements but I wouldn't think it would cause them all to contaminate.
Edited by plutoniusspasticus (08/19/20 04:52 PM)
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26888801 - 08/19/20 04:40 PM (3 years, 5 months ago) |
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I may touch the arm holes but I don't rest on them. I don't think I bumped it last time.
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tryptkaloids
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Are you letting your PC vent steam for 10 min before putting the weight on?
-------------------- "Remember, kids, the difference between science and screwing around is writing it down" -adam savage Flowchart for Recommended plan of action. Learn the tried and true way to grow mushrooms Use the Damn search engine After you know what you're doing, take a break Pick a book, Make some chips! Josex said:Don't take the site seriously bro, ain't worth it.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26888851 - 08/19/20 05:05 PM (3 years, 5 months ago) |
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I just followed the instructions for my pc. It said to put the weight on and wait for a gentle hiss and then lower the heat. It didn't say to do that.
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tryptkaloids
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What size and brand? You should do that with prestos forsure, but that's all ive ever used
-------------------- "Remember, kids, the difference between science and screwing around is writing it down" -adam savage Flowchart for Recommended plan of action. Learn the tried and true way to grow mushrooms Use the Damn search engine After you know what you're doing, take a break Pick a book, Make some chips! Josex said:Don't take the site seriously bro, ain't worth it.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26889398 - 08/20/20 03:06 AM (3 years, 5 months ago) |
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I've got a prestige 6 liter. I'll double check the manual.
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tryptkaloids
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Maybe make a post specific to that pc and see if anyone knows forsure
-------------------- "Remember, kids, the difference between science and screwing around is writing it down" -adam savage Flowchart for Recommended plan of action. Learn the tried and true way to grow mushrooms Use the Damn search engine After you know what you're doing, take a break Pick a book, Make some chips! Josex said:Don't take the site seriously bro, ain't worth it.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26889975 - 08/20/20 11:57 AM (3 years, 5 months ago) |
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I may do that at some point. However I don't really think it's the pressure cooker. I've made clean stuff in the past doing the same thing. It seems like the problem is to do with the sab/misting/technique. I'll have to keep trying bearing in mind what people have said.
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tryptkaloids
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2 hours seems like a long time to let it cool, let the pressure lock fall and use it when it's handleable
-------------------- "Remember, kids, the difference between science and screwing around is writing it down" -adam savage Flowchart for Recommended plan of action. Learn the tried and true way to grow mushrooms Use the Damn search engine After you know what you're doing, take a break Pick a book, Make some chips! Josex said:Don't take the site seriously bro, ain't worth it.
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Spore211215
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26890420 - 08/20/20 05:11 PM (3 years, 5 months ago) |
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I've PC'd my agar cups and left them for upwards of 16+ hrs after PCing was done so i don't think that's his issue unless hes not getting enough pressure. My quick googling for his PC didnt show what pressure his rig can get to. Could he just need to PC for longer because the pressure might be lower?
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tryptkaloids
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Re: Petri dishes keep contaminating [Re: Spore211215]
#26890433 - 08/20/20 05:18 PM (3 years, 5 months ago) |
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Those are sealed. These have to be poured hot. There is a difference between pasty plates that can be left unwrapped for months and Petri dishes that have to be wrapped or they'll get dirty
-------------------- "Remember, kids, the difference between science and screwing around is writing it down" -adam savage Flowchart for Recommended plan of action. Learn the tried and true way to grow mushrooms Use the Damn search engine After you know what you're doing, take a break Pick a book, Make some chips! Josex said:Don't take the site seriously bro, ain't worth it.
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Spore211215
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26890454 - 08/20/20 05:33 PM (3 years, 5 months ago) |
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Ok yeah that's fair. Ive recently been thinking about upping my agar game to more efficiently get plates out so my horizons on it aren't that broad yet. Should he maybe change up his style to the pasty plates and see if he still has issues? i know that doesn't solve the issue at hand but could make the contam rates possibly go down and work his way up from there.
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LadysKnight
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Re: Petri dishes keep contaminating [Re: Spore211215]
#26890462 - 08/20/20 05:40 PM (3 years, 5 months ago) |
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Fwiw, I normally let my pre-pour glass petri plates cool in the PC for 24-48 hrs before using.
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tryptkaloids
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Re: Petri dishes keep contaminating [Re: LadysKnight]
#26890729 - 08/20/20 08:41 PM (3 years, 5 months ago) |
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Not everyone has glass plates they can sterilize at home
-------------------- "Remember, kids, the difference between science and screwing around is writing it down" -adam savage Flowchart for Recommended plan of action. Learn the tried and true way to grow mushrooms Use the Damn search engine After you know what you're doing, take a break Pick a book, Make some chips! Josex said:Don't take the site seriously bro, ain't worth it.
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normalperson
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Your PC only reaches 10PSI
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: Spore211215]
#26891183 - 08/21/20 07:22 AM (3 years, 5 months ago) |
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https://www.amazon.co.uk/ask/questions/asin/B0007U94U0/3/ref=ask_ql_psf_ql_hza?isAnswered=true This is my pc. If you search the q and a it says it goes to 15 psi. I kind of assume 15 lb = 15 psi.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: Spore211215]
#26891188 - 08/21/20 07:28 AM (3 years, 5 months ago) |
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That's a good idea. It's a way to pin point if the contam is my pressure cooker or technique. Btw, do you know of a good alternative in the UK? I've looked into pasty plates before but I couldn't be sure of a UK equivalent.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26891192 - 08/21/20 07:31 AM (3 years, 5 months ago) |
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I do have some glass petri dishes but from what I've seen/heard glass no pour isn't great. I want to stick with plastic for now and solve my current contam issue.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: normalperson]
#26891196 - 08/21/20 07:34 AM (3 years, 5 months ago) |
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tryptkaloids
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Anything labeled with recycling code 5 should be fine. They have a little recycling triangle with a 5 in it and "pp" for polypropylene 5
-------------------- "Remember, kids, the difference between science and screwing around is writing it down" -adam savage Flowchart for Recommended plan of action. Learn the tried and true way to grow mushrooms Use the Damn search engine After you know what you're doing, take a break Pick a book, Make some chips! Josex said:Don't take the site seriously bro, ain't worth it.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26892851 - 08/22/20 03:16 AM (3 years, 5 months ago) |
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Okay. Just ordered some containers.
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normalperson
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i looked up the wrong model, you are correct. your's does reach 15psi.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: tryptkaloids]
#26911162 - 09/01/20 04:07 AM (3 years, 4 months ago) |
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I've determined the problem isn't my pc because I make no pour jars 100% every time. I mist once and wait for 15-20 minutes for it to settle. For some reason I'm only getting around 40% success rate with my pours. Should I upload a video of me pouring to check my technique? I'm really struggling to find the problem.
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A.k.a
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It’s gotta be either pouring technique or air can get into whatever you’re using as a plate.
If you have plastic petris the best method I’ve found is to take a stack of five and lift up everything but the bottom dish and pour the agar in, then set the stack back down and pick up the next one and do it again working your way up. Once I do the first five I stack more on top. I used to just start with a stack of 15 but it’s a pain in the ass lifting that many to do the first ones.
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plutoniusspasticus
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Re: Petri dishes keep contaminating [Re: A.k.a]
#26911586 - 09/01/20 10:12 AM (3 years, 4 months ago) |
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Quote:
A.k.a said: It’s gotta be either pouring technique or air can get into whatever you’re using as a plate.
If you have plastic petris the best method I’ve found is to take a stack of five and lift up everything but the bottom dish and pour the agar in, then set the stack back down and pick up the next one and do it again working your way up. Once I do the first five I stack more on top. I used to just start with a stack of 15 but it’s a pain in the ass lifting that many to do the first ones.
I've used a bunch of different containers i.e. glass petris,jars and plastic petris. There doesn't seem to be a difference with contamination so I don't think it's about air getting in.
I've tried your technique in the past which was the time it ended up 100% contam. Tbh, It seems strange that it would be my technique either considering the relatively lazy technique I've seen on youtube.
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tryptkaloids
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Quote:
plutoniusspasticus said: I've determined the problem isn't my pc because I make no pour jars 100% every time. I mist once and wait for 15-20 minutes for it to settle. For some reason I'm only getting around 40% success rate with my pours. Should I upload a video of me pouring to check my technique? I'm really struggling to find the problem.
Would definately be a good idea
Check the filters on your no-pour
-------------------- "Remember, kids, the difference between science and screwing around is writing it down" -adam savage Flowchart for Recommended plan of action. Learn the tried and true way to grow mushrooms Use the Damn search engine After you know what you're doing, take a break Pick a book, Make some chips! Josex said:Don't take the site seriously bro, ain't worth it.
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