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panne cyanne
albino queen


Registered: 04/15/20
Posts: 145
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Re: Uv-c to sterilize agar [Re: AndyHinton]
#26653394 - 05/06/20 05:39 PM (3 years, 9 months ago) |
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Quote:
There's no special instructions beyond wiring a lightbulb, using the thickest PP/PET possible, closing the sash while the bulb is lit, and avoiding ozone bulbs.
AND of course, dodging the light itself when in use.
you guys REALLY need to read up on blue light hazards. these things arent a casual lab tool.
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AndyHinton


Registered: 12/05/16
Posts: 434
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Anyway, I did some more research. Quality UV-C bulbs are the only ones I recommend because they emit true 254 nm waves. See UV Properties of Plastics: Transmission and Resistance.
This is important because most plastics and glass thicker than 0.5 mm can't pass UV-C spectra. They can only pass high-energy visible light such as UV-A and UV-B, around 300 to 500 nm. Regular window glass is enough to block UV-C. It's necessary to make UV-C bulbs from quartz for this reason.
Some plastics and glass are better than others at absorbing UV waves: acrylics and borosilicate, respectively. Both known for their thickness and vitrified molecular structure. The purer and less homogenized a compound is, the better it will pass UV-C waves. So not a 3 mm thick polypropylene box made in China for mass consumption. You would need something like a dichroic mirror to selectively pass UV-C waves.
When emitted at high power, UV-C catalyzes oxygen to make ozone. That's why bodhisatta's workplace smells bad: 6 kW UV-C spontaneously making ozone. It's also why the late ozone layer was so high up in the atmosphere: UV-C waves were among the first blocked.
The National Weather Service has a good explanation re: calculating the UV index. UV-C is dangerous because it's strongly ionizing, but it's effectively blocked by plastic and glass. The real danger lies in fake bulbs on Amazon that simulate the effect with UV-B and ozone.
Obviously, my bulb emits more than just 254 nm and some of those waves will pass through. So hanging around the light isn't advised, nor is staring at it. Common sense for an uncommon crowd. 
A fun fact: gamma irradiation uses Cobalt-60 to sterilize equipment with the gamma rays the radioactive isotope emits.
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panne cyanne
albino queen


Registered: 04/15/20
Posts: 145
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Re: Uv-c to sterilize agar [Re: AndyHinton]
#26653774 - 05/06/20 08:06 PM (3 years, 9 months ago) |
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dont mind me. just worked in a light physics lab for over a decade that often did work with biologicals and blue light of various power levels and wavelengths.
if you can see it, and its below 300nm. show extreme caution.
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bodhisatta 
Smurf real estate agent


Registered: 04/30/13
Posts: 61,890
Loc: Milky way
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 Don't go outside in the sun then.
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AndyHinton


Registered: 12/05/16
Posts: 434
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Re: Uv-c to sterilize agar [Re: bodhisatta]
#26654482 - 05/07/20 06:24 AM (3 years, 9 months ago) |
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Now I'm curious to know the exact UV transmittance of my tub's PP formulation. So I bought a UV radiometer. We'll have a precise answer soon. The meter's spectral response curve is below.
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Edited by AndyHinton (05/07/20 06:41 AM)
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brikogen
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Re: Uv-c to sterilize agar [Re: AndyHinton]
#26655309 - 05/07/20 02:42 PM (3 years, 9 months ago) |
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Quote:
AndyHinton said: Now I'm curious to know the exact UV transmittance of my tub's PP formulation. So I bought a UV radiometer. We'll have a precise answer soon. The meter's spectral response curve is below.

It seems to have little to no sensitivity at the low end of the UV spectrum where the UV-C range is located?
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AndyHinton


Registered: 12/05/16
Posts: 434
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Re: Uv-c to sterilize agar [Re: brikogen]
#26657321 - 05/08/20 12:19 PM (3 years, 9 months ago) |
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Yes. Because we already know about UV-C's poor transmittance through common plastics, and because I only need one such device. UV-C meters with remote probes cost almost $450 new and are difficult to find used.
The question I want to answer is, "What's the relative full-spectrum UV intensity just outside the tub, vs. one foot away from it, vs. ambient sunlight and shade?" That's my intended purpose.
Other answers involving the fractionation of UV spectra are assumed to be fully funded by the inquirer, i.e., buy a Solarmeter 8.0-RP if you want to measure UV-C. I would send you plastic samples to test.
Another quick fact. UV-C lamps are visibly purple for the same reason flammable gases are adulterated with bad-smelling compounds: to indicate the presence of a potential hazard.
See also
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Edited by AndyHinton (05/08/20 11:24 PM)
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panne cyanne
albino queen


Registered: 04/15/20
Posts: 145
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Re: Uv-c to sterilize agar [Re: AndyHinton]
#26658049 - 05/08/20 06:09 PM (3 years, 9 months ago) |
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Quote:
AndyHinton said: the presence of a potential hazard.
im comfortable with trained professionals in proper labs using these things as needed. i would really hate to see an army of noobs with these things installed in apartments, frat houses, trailers, barns, bedrooms,crawl spaces, and attics.
especially if they realized you can get these things powerful and cheaply.
of course, the whole hobby has its hazards. blue light is pry not the worst of them. but if UV is needed, i would always opt for the most cautious minimum, and absolutely wear UV safety glasses.
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bodhisatta 
Smurf real estate agent


Registered: 04/30/13
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Loc: Milky way
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Ok, if y'all want ill try sterilizing agar with UV

These are are 6000 watts. They produce ozone. Even though it's not shown on the graph. There are ozone free variants available for more money but the units are very ventilated just to operate anyway
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panne cyanne
albino queen


Registered: 04/15/20
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Re: Uv-c to sterilize agar [Re: bodhisatta]
#26658082 - 05/08/20 06:22 PM (3 years, 9 months ago) |
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yowza bod. that would tan an entire sorority in one flash.
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AndyHinton


Registered: 12/05/16
Posts: 434
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Quote:
panne cyanne said: i would really hate to see an army of noobs with these things installed in apartments, frat houses, trailers, barns, bedrooms,crawl spaces, and attics.
Yeah. I think a big danger lies in peeps buying cheap Amazon shit thinking it emits true UV-C waves. They hear that plastic blocks it. But there's a cross point between the bulb's UV emissions and the spectra the plastic will pass. Unique to each setup and with 99.97% not testing it. We'll know next week for a true 15W bulb and about 3 mm thick PP5, at least.
I get a feeling of ominous presence when the light is on, a power to respect. Orange glasses and not being close to it. It's so easy to avoid unnecessary UV exposure. But I've also seen herbs on fitness YouTube irradiating their balls with infrared to "increase testosterone" (and free radicals as by-products of overactive metabolism).
This is all temporary until I can get back to my UV-equipped flow hood. Where the bulb in question is from, an MIT cancer lab. But the radiometer will be useful beyond testing how hot tub is with a ghetto, exposed wires UV bulb taped inside. The new age is here, it's all about the molecules.
PS. You can make a stencil over a plate, spread yeast evenly, and incubate it with UV light overhead to make photo-quality agar art. @yeastograms
Edited by AndyHinton (05/08/20 11:27 PM)
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brikogen
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Re: Uv-c to sterilize agar [Re: bodhisatta]
#26658965 - 05/09/20 01:30 AM (3 years, 9 months ago) |
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Quote:
AndyHinton said:
Quote:
panne cyanne said: i would really hate to see an army of noobs with these things installed in apartments, frat houses, trailers, barns, bedrooms,crawl spaces, and attics.
Yeah. I think a big danger lies in peeps buying cheap Amazon shit thinking it emits true UV-C waves. They hear that plastic blocks it. But there's a cross point between the bulb's UV emissions and the spectra the plastic will pass. Unique to each setup and with 99.97% not testing it. We'll know next week for a true 15W bulb and about 3 mm thick PP5, at least.
I get a feeling of ominous presence when the light is on, a power to respect. Orange glasses and not being close to it. It's so easy to avoid unnecessary UV exposure. But I've also seen herbs on fitness YouTube irradiating their balls with infrared to "increase testosterone" (and free radicals as by-products of overactive metabolism).
This is all temporary until I can get back to my UV-equipped flow hood. Where the bulb in question is from, an MIT cancer lab. But the radiometer will be useful beyond testing how hot tub is with a ghetto, exposed wires UV bulb taped inside. The new age is here, it's all about the molecules.
PS. You can make a stencil over a plate, spread yeast evenly, and incubate it with UV light overhead to make photo-quality agar art. @yeastograms
Why bother with the uncertainty, just cover the box with a towel or light blocking cloth before you switch it on. But I'm more curious though about PP degradation rate when using this. I'm quite happy with my SAB but how fast would it turn it into nacho chips compared to how much you use this.
Also you don't really need a radiometer to check if UV-C is being emitted from your bulb. Just contaminate the shit out of some plates and put them in the chamber. Then set them aside and see what grows on them. If they stay clean then your lamp is good to go.
Quote:
bodhisatta said: Ok, if y'all want ill try sterilizing agar with UV

These are are 6000 watts. They produce ozone. Even though it's not shown on the graph. There are ozone free variants available for more money but the units are very ventilated just to operate anyway

The agar plate that that can sterilize is probably the size of a football field.
Edited by brikogen (05/09/20 02:25 AM)
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bodhisatta 
Smurf real estate agent


Registered: 04/30/13
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Loc: Milky way
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Re: Uv-c to sterilize agar [Re: brikogen]
#26659393 - 05/09/20 07:25 AM (3 years, 9 months ago) |
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I actually doubt it will work but..
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AndyHinton


Registered: 12/05/16
Posts: 434
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Re: Uv-c to sterilize agar [Re: bodhisatta]
#26659550 - 05/09/20 09:07 AM (3 years, 9 months ago) |
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Yeah. Going by the spectrals, that looks like a yellow and purple light with incidental UV-A emission. But at that power you could probs fry any stray yeasts.
Ideally the bulb would have a peak response close to 254 nm, the smallest amplitude possible, and a bit of visible purple light for safety reasons. The 254 nm target is important because that's peak DNA absorption, meaning the fastest death by DNA scrambling.
This kind of power is really cheap and available, maybe 20€ per bulb. Here are the curves for the Philips TUV T8, and a general reference spectrum. The Sankyo Denki G15T8 currently installed in the flow hood is similar.

If I had to give the technology to a moron and protect them from themselves, it's a hard choice. I really don't know if I'd give them a truly deadly bulb with tight but easily controlled UV-C emissions, or a fake Amazon bulb that vomits UV-B like a tanning salon.
Also, can we please stop talking about UV-C agar sterilization? It can never match the power efficiency of a real autoclave and it's just bad technique.
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Edited by AndyHinton (05/09/20 09:26 AM)
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bodhisatta 
Smurf real estate agent


Registered: 04/30/13
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Re: Uv-c to sterilize agar [Re: AndyHinton]
#26659693 - 05/09/20 10:16 AM (3 years, 9 months ago) |
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Quote:
AndyHinton said: Yeah. Going by the spectrals, that looks like a yellow and purple light with incidental UV-A emission. But at that power you could probs fry any stray yeasts.
Ideally the bulb would have a peak response close to 254 nm, the smallest amplitude possible, and a bit of visible purple light for safety reasons. The 254 nm target is important because that's peak DNA absorption, meaning the fastest death by DNA scrambling.
This kind of power is really cheap and available, maybe 20€ per bulb. Here are the curves for the Philips TUV T8, and a general reference spectrum. The Sankyo Denki G15T8 currently installed in the flow hood is similar.

If I had to give the technology to a moron and protect them from themselves, it's a hard choice. I really don't know if I'd give them a truly deadly bulb with tight but easily controlled UV-C emissions, or a fake Amazon bulb that vomits UV-B like a tanning salon.
Also, can we please stop talking about UV-C agar sterilization? It can never match the power efficiency of a real autoclave and it's just bad technique.
It doesn't peak in the ozone producing territory but it does produce enough ozone that it requires two three phase blowers to cool the bulbs and evacuate the ozone
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bodhisatta 
Smurf real estate agent


Registered: 04/30/13
Posts: 61,890
Loc: Milky way
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Re: Uv-c to sterilize agar [Re: bodhisatta]
#26659698 - 05/09/20 10:18 AM (3 years, 9 months ago) |
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I think the cap will melt or get fucked long before the agar sterilizes. I would use a Pyrex media bottle
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brikogen
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Re: Uv-c to sterilize agar [Re: AndyHinton]
#26659709 - 05/09/20 10:28 AM (3 years, 9 months ago) |
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Quote:
AndyHinton said: Also, can we please stop talking about UV-C agar sterilization? It can never match the power efficiency of a real autoclave and it's just bad technique.
I thought the OP was about sterilizing agar surfaces. I agree that it may encourage bad technique but the idea has some merit. Since UVC sterilization is only a surface treatment it can not replace an autoclave. However it can be used to sterilize agar containers and lids that are not autoclavable, before you pore your sterile agar. Why would you do that? Well perhaps you care about the planet and don't want to add to the pile of plastic waste of the world. Perhaps by using biodegradable containers (paper, PLA, sugarcane...).
But hey what the fuck do I know
Edited by brikogen (05/09/20 10:28 AM)
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AndyHinton


Registered: 12/05/16
Posts: 434
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Re: Uv-c to sterilize agar [Re: brikogen]
#26659725 - 05/09/20 10:37 AM (3 years, 9 months ago) |
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Quote:
bodhisatta said: It doesn't peak in the ozone producing territory but it does produce enough ozone that it requires two three phase blowers to cool the bulbs and evacuate the ozone
That's exactly what I'm trying to avoid: work smarter not harder. This UV-C sterilization is all about peak target emissions from cool bulbs.
My city runs nightly infrared helicopters over my neighborhood. I can't afford to run an Olympic tanning salon just to kill some airborne spores. A knock on the door, a roommate unwittingly invites them in, me with a scientist's tan and a jar of the fuzzy white. I swear officer, it's shaggy mane and oyster truffles. I'm actually expecting crops of both soon, rare flavors indeed. 
Quote:
brikogen said: I thought the OP was about sterilizing agar surfaces. I agree that it may encourage bad technique but the idea has some merit. Since UVC sterilization is only a surface treatment it can not replace an autoclave. However it can be used to sterilize agar containers and lids that are not autoclavable, before you pore your sterile agar. Why would you do that?
It's a bad idea either way. Also, UV-C can't replace gamma rays. Sterile tubes come that way because they're bathed in radioactive decay. My whole setup is optimized for low waste and unsuspicious material flow anyway.
I'm using Mason jelly jars with unmodded PP5 lids, unmodded Ziploc PP5 pints, unmodded mini tubs, and bulk food. Disposables are mostly toothpicks and cotton swabs, and occasional Parafilm backing, pipette tips, and centrifuge tubes. Easy to transport and compost bio waste.
Edited by AndyHinton (05/09/20 10:58 AM)
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AndyHinton


Registered: 12/05/16
Posts: 434
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Re: Uv-c to sterilize agar [Re: AndyHinton]
#26667060 - 05/12/20 04:50 PM (3 years, 9 months ago) |
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Anyway, the extraneous UV waves coming directly off the bulb measured 300 µW/cm2 or basically nothing. This is easily explained by the meter's slight UV-C sensitivity and minor errors in the bulb manufacturing process.
In contrast, daylight measured around 2,000 µW/cm2 when pointed directly at the setting sun. I'll probably buy a Solarmeter 8.0 to measure the life of my bulb and resell this one cheap.
tl;dr: Spend some extra money on a good lamp from a manufacturer that provides spectral curves. If there are no curves then the lamp isn't real. UV-C is a great for sterilizing a dead air box provided you aren't stupid about it. Wear amber glasses and don't irradiate your nuts. Have some respect for this powerful force that only comes naturally from stars.
Edit: Maybe in the long run I should invest in a mass flowmeter and a UV-C radiometer. I'm all about not guessing important facts like the efficacy of my HEPA filter and UV-C bulb. Because this stuff must be regularly replaced. A longtime gripe I've had with FP-style flow hoods not designed for easy filter replacement. Manufacturers may try to enforce this but their assumptions are often absurd, e.g., 1,000 user-configurable "hours" (30 min default) on a UV-C bulb whose lifetime is rated at 7,500 hours. Best to just certify it myself.
Edited by AndyHinton (05/12/20 06:16 PM)
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Celestialexplorer1



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Re: Uv-c to sterilize agar [Re: AndyHinton]
#26668056 - 05/13/20 06:30 AM (3 years, 8 months ago) |
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In the beginning I had labeled this idea only as a further step to pressure cook and sterility technique. It was only meant as a possible extra safeguard against contaminates, obviously this or nothing else could replace good sterile techniques such as a pressure cooker, flow hood, sab, clearing surfaces before work, etc. but I thought of this as a maybe. Just want to make sure that is kept in mind
And for the record I never told anyone to use uv-c to sterilize agar. For the record.
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 To spend just one moment in eternity
Edited by Celestialexplorer1 (05/13/20 06:42 AM)
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