What is Water Activity? – OSP 03

Graham and Ashkahn are BACK! 

The newly monikered Occasional Solutions Podcast hits the ground running to share some big news about Water Activity. The Float Boys bring their banter to bear to the benefit of you, buds. Thanks to information and collaboration with Roy Vore, they found a way to measure the way pathogens spread through float tank water. 

Listen now to hear them dive into the nitty-gritty of new research on float tank water! You don’t wanna miss this. 

Getting Salty With Speakers: Roy Vore – DSP 226

Are Alligators More Aggressive Than Crocodiles?

Float Solution Water Activity Test 2019.04.29

Water Activity Table

25°C is 77 °F

25°C is 75.02 °F

(fun fact: at lower temperatures, an easy way to convert Celsius to Fahrenheit is to double it then add 30. For Fahrenheit to Celsius, just subtract 30 and halve it).

Listen to Just the Audio

Transcription of this episode… (in case you prefer reading)

Graham: Look who’s here.

Ashkahn: Oh, boy, this is exciting, guys.

Graham: Coming at you live through your headphones/phone/speaker system/car stereo.

Ashkahn: Yeah.

Graham: That was an and/or kind of proposition. It could be all of them at once with modern technology.

Ashkahn: So this is the first time we’re doing a classic Daily Solutions episode here, where we’re just…

Graham: Only it’s not daily.

Ashkahn: Yeah, and we’re not really… It’s very little… not really a solution, it’s not really a solution, either, is the other thing. But it is a podcast, that much for sure we’re still doing.

Graham: One-third, we’re one-third there.

So, we decided when we stopped doing the Daily Solutions podcast that it would be fun to hop on the air when we had actual important things to discuss.

Ashkahn: Yeah, turns out that’s not very often-

Graham: Obviously.

Ashkahn: … but it does happen every once in a while.

Graham: And this is one of those times.

Ashkahn: Yeah.

Graham: So, here we are.

Ashkahn: And we’ve got some news.

Graham: We have news. Hit it.

Ashkahn: Okay, yeah, this is it, guys.

Graham: Hit it.

Ashkahn: This is happening.

Graham: Hit them with it.

Ashkahn: We’ve been trying to figure stuff out with float-tank sanitation for some time.

Graham: All right, hope you guys enjoyed the episode, it’s a good one. We’ll check back in when we find out the results.

Ashkahn: Yeah, this is really important. This is kind of just like a constant in the background thing that we pay attention to the sanitation stuff, and you’ve heard us give episodes about regulations and that sort of thing. And over the last little bit, there’s been this concept that has come to mind as something that may be relevant to float tanks, and it’s this concept called water activity, or water availability.

Ashkahn: This is something that Roy Vore, the microbiologist, who is kind of the main recreational-water illness dude in the pool and spa world.

Graham: He’s the guy.

Ashkahn: He’s the guy, and he’s been working on float-tank stuff with us, and-

Graham: We’ll link to his talk, by the way, in the show notes. He gave a great float conference talk.

Ashkahn: We’ll put his talk. We also-

Graham: Yeah, yeah.

Ashkahn: He’s been really the one who kind of brought up this idea of water activity as something that we should really look into. It’s been brought up before, too, over the course of people talking about what kind of pathogens could survive in this kind of salt. This is that question, what things can survive in salt. This is a big factor in terms of what makes things survivable or not.

Graham: Yeah, we found some ancient tablets by the Dead Sea that referenced it, we think.

Ashkahn: Yeah, some rules around there.

Graham: Not exactly sure about those.

Ashkahn: So, Roy actually… We did a podcast episode for Daily Solutions with him, as well as the float conference podcast last year, and we talked about this concept of water activity in there. So if you want to hear more about Roy talking about it, we’ll link those two episodes in the show notes, as well.

Graham: That’s true, along with what is the more dangerous animal, an alligator or a crocodile?

Ashkahn: Yeah, that factoid will be presented to you in the show notes.

Ashkahn: Here’s the interesting thing, though. So we’ve been talking about water activity, and I’ll explain the basics of water activity in a moment and how much could survive in float tanks because of its water activity, basically because the amount of salt that’s in there. And through all this discussion, we’ve never actually known what the water activity of a float tank, of Epsom salt-saturated solution is, because the data has never existed. There’s data out there for sodium chloride at saturation, and things like that-

Graham: Which makes sense, because it pops up a lot in cooking, and you eat it and put it in water and it makes sense.

Ashkahn: And so, Roy and I both looked and there was just nothing we could find on the internet that had this data. And so really the kind of cool news that we’re sharing here is that we managed to get some data on it.

Graham: We did it!

Ashkahn: We did it.

Graham: We found data.

Ashkahn: We fixed the whole float industry with a single thing. So, yeah, we actually found a little lab here in town and took in a sample of float-tank water, and got some results. So, that’s kind of exciting stuff.

Graham: What kind of lab was it, by the way, that we found?

Ashkahn: It was a food lab, and so that is a great segue, Graham, into-

Graham: Oh, thank you.

Ashkahn: … what water activity really is, and where this concept comes from.

Graham: Oh, I thought you meant my new Segway.

Ashkahn: No, that thing’s horrific, you should get rid of that.

Graham: But I got a helmet. Go on.

Ashkahn: So, basically, this concept is used very widely in the world of food, because it’s kind of like when you… it’s like how much water is available in a liquid. And different microorganisms can only survive or only grow if there’s enough water available to them in the kind of solution that they’re in. Otherwise, weird thing happen, right? Like if they don’t have enough water, sometimes it will change the pressure within a microorganism’s cell and it will cause the cell to implode, or for other very science-y reasons they just can’t survive in different things.

Graham: Super science-y, by the way.

Ashkahn: And this comes up, because they use this as a method of food preservation all the time. This is what putting salt onto various meats for curing and preserving them is. It’s about water activity, and this is what the pickling process is, or kimchi, or honey. This is why honey is naturally antibacterial and has no shelf life.

Graham: Yeah, you might’ve heard of people finding jars of honey in ancient Egyptian tombs and it’s still theoretically good. That’s why, is because…

Ashkahn: It just has a really low water activity.

Graham: Yeah, and nothing that would be harmful to us can survive in something with that low water activity.

Ashkahn: So the water activity of water is one, that’s the kind of reference point. And so things that are lower than one have a lower available water, water activity, and typically that means the lower and lower it gets, the harder and harder it is for most things to grow or survive in them.

Ashkahn: And just to give you some reference points, I have a little table that Roy Vore pooled some research on of different numbers of certain pathogens and what their required water activity for growth is. So, again, compared to distilled water which has a water activity of one-

Graham: And super water which is at like two.

Ashkahn: Yeah, ultra water.

Graham: I wasn’t going to mention it because I didn’t want to confuse people, but-

Ashkahn: There’s twice the water in the same mass. It’s pretty impressive.

Graham: Stuff loves it, too, microorganisms grow like crazy in there.

Ashkahn: So, pseudomonas, which is this kind of like skin disease that is colloquially called hot-tub rash, big kind of common pool illness, that requires a water activity of point .97 to be able to grow. That’s its minimum for growth. And E. coli is a little bit below that, a .95, then we have other things like candida at .87, staph at .86, et cetera, et cetera, on down.

Ashkahn: Then we have a couple other reference points that we found online about sodium chloride. So actually a 20% sodium chloride solution, and temperature does affect water availability, as well. So a 20% sodium chloride at 35 degrees Fahrenheit has a water activity of about .83, a saturated sodium chloride at 35 degrees Fahrenheit has about a .75 water activity.

Ashkahn: And so this is kind of the thing that we’re trying to figure out where float tanks sit in this sort of spectrum to see what things probably are not going to have a very easy time growing in there, maybe surviving, and what things will be able to tolerate the levels of salt that are in there.

Ashkahn: I’ll explain how we pooled this data in a second, but to not create any more suspense, the actual number that we ended up getting was about .94 for the Epsom salt solution.

Graham: So if you’re trying to remember every point that Ashkahn said before that, for what diseases or bacteria are higher or lower, you’re out of luck because we’re definitely not going to post that up on the show notes.

Ashkahn: That’s not going anywhere. You should’ve been writing these down. I’m assuming most people, when they listen to our podcast, have notebooks and pencils in front of them.

Graham: Yeah, a chalkboard. You get the paint-on chalk for your dashboard when you’re driving so you can just take notes.

Ashkahn: Glasses if you need them or not. You’re just wearing them to make this seem all smart.

Graham: It’s like, “Why? Why are they wearing the glasses?”

Ashkahn: Okay. So, yeah, just to kind of roughly put those in reference. So we have magnesium sulfate came in at a lower water activity than pseudomonas and E. coli need to be able to grow. And actually a much higher water activity than those sodium chloride numbers I read you.

Graham: Did you say sodium chloride initially?

Ashkahn: When, just now?

Graham: Yeah, I think you meant to say magnesium sulfate.

Ashkahn: Oh. Okay, well if I did, if I said it wrong, we’ll go back and edit it, and then it’ll be like I said it right the whole time.

Graham: All right, well, we’re going to have to do it, because you didn’t say magnesium sulfate.

Ashkahn: Okay. We’ll sort this all out later.

Ashkahn: The magnesium sulfate at .94 is decently higher than the sodium chloride numbers that we were getting, so that 20% sodium chloride or saturated sodium chloride solution was at .75. So, when we’re comparing table salt to Epsom salt, there actually is a pretty decent difference, despite there probably being by volume somewhat a similar amount of salt.

Graham: Which is kind of surprising. We actually expected to have a lower water availability for our float-tank water, as a result of that.

Ashkahn: We were expecting it to be more like sodium chloride, and it turns out it’s decently different.

Graham: So, that’s not terrible news, because it still comes in at that nice low level for, again, things like pseudomonas, things like E. coli. But it is a little bit unfortunate in that the lower it is, theoretically, the less stuff can grow in there, so the less we’re worried about it, just in terms of only that water availability scale.

Ashkahn: Basically we ran a test twice at this lab, and the actual numbers we got were .936 and .933, so that kind of averages out to .935. And the temperatures was a slightly interesting one there. I actually got to go to this lab and do it, it was really awesome. It was the Food Innovation Center here in Portland, which is part of Oregon State University.

Ashkahn: I emailed them and said I had this weird project. They’re used to just doing this for food stuff. The lab guy who worked there was super nice and told me to come in, and I got to just go back into their whole area. I actually made the float-tank solution on site there using distilled water. I took a pot and mixed up a fresh batch of Epsom salts. I used USP Epsom salt, I used distilled water from their distilled-water tap, I mixed it up on-site, and I got it to 1.27 specific gravity, that’s the specifics of this.

Graham: Pun intended there with specifics?

Ashkahn: Yeah, that’s the specifics. Also Roy Vore told me that in the industry, they call specific gravity “speegee”.

Graham: Which we need to immediately adopt for our industry, as well.

Ashkahn: He might be trying to prank me, that’s a distinct possibility, but he said they call it the speegee, like, “What’s the speegee on that thing?” So we’re going to just adopt that from here on.

Graham: I’m rolling with it, because if he’s pranking it, it’s a way more hilarious thing to call it, anyway.

Ashkahn: I took it up to the old 1.27 speegee. The interesting thing was their machine, you basically just take a little sample of this. It’s a tiny cup, it’s got to be maybe a quarter of an ounce or something, and you put this little cup into this machine and it reads off the water availability. I don’t know exactly how it works, it’s something about the-

Graham: Very science-y.

Ashkahn: … evaporation point? It heats up and it detects the point that it starts condensating or evaporating off onto this other layer in there. *Mumble Mumble* then you can determine the water-

Graham: Then the science happens.

Ashkahn: … activity from that.

Graham: And then it says the water activity is .9235.

Ashkahn: So, yeah, I balanced it all out, I got it to float-tank temperature. I was trying to be real careful and measure things and get it just right when I put it in there, which was really hard because as soon as I piped it in that small of a quantity, just that process dropped like five or six or seven degree Fahrenheit off of it, which is interesting. But I still got it in there around float-tank temperature, and then the machine was like, “The sample’s too hot, we can’t measure that.” And it just refused to actually start the test until the thing cooled down a little bit.

Ashkahn: So, yeah, what I don’t know is the specific gravity at 1.27-

Graham: Speegee.

Ashkahn: Speegee. I don’t know the speegee at 1.27 speegee at 93.5 degrees Fahrenheit, or 94 degrees Fahrenheit. So it would have to cool to almost in the 70-degree range to be able to have the machine turned on. And then the machine at the end to its test tells you the temperature that the sample ended at, I think. It displays both the water activity and the temperature.

Ashkahn: And so the two tests I did were at 25 degrees Celsius, and 23.9 degrees Celsius, which in Fahrenheit is-

Graham: Put it in the show notes.

Ashkahn: Yeah, it’s a bigger number than that, at least.

Graham: We know that much.

Ashkahn: Actually, no, I wrote it down here, let’s see. It’s about 76 degrees Fahrenheit.

Graham: Definitely bigger, we were right.

Ashkahn: Yeah. We should be scientists. So, that’s kind of one interesting thing. This was more at about 76 degrees, I don’t really know exactly how much the temperature was going to effect it. It was about one degree Celsius different between them, and the one that was at 25 degrees Celsius was the one that came in slightly higher in water activity. I don’t know. I doubt the proper temperature is going to make a gigantic deal, it’s not going to get us down to the .75 of sodium chloride or something like that, but it might make a marginal difference.

Ashkahn: And so I had this document now that they gave me that explains… Just a little one page thing that shows the results and the specifics from the lab, which is pretty cool, so we’ll put that in the show notes, as well.

Graham: Yep, and we’ll be adding it to the Health Department essentials, as well, along with all of the other nice resources to present to health regulators if you’re at that stage in your journey.

Ashkahn: And that’s exciting.

Graham: It is actually really exciting stuff.

Ashkahn: That’s basically the deal. I honestly don’t know enough about this stuff to feel comfortable telling you this is conclusive proof that E. coli can’t survive in a float tank.

Graham: Of anything really, yeah.

Ashkahn: Just interpret this for what it is. This is data that we’re going to be able to hand off to microbiologists down the line, and they’re going to be able to use this as part of a better analysis. We’re filling in part of the picture. We have more information to help us understand what the salt is doing in there, and how it’s helping us, and what things it could help us against, and what things it can’t.

Ashkahn: We can test this more. It actually wasn’t really that expensive of a test to run, which is really cool. So if we need to run more studies in this nature, get more data, or try to even pool more samples, that’s totally possible. I got an in with the lab now.

Graham: Yeah, hook them up with a couple free floats on the side.

Ashkahn: I did do that, actually.

Graham: Yeah, of course, that’s the game.

Ashkahn: And it was hilarious being in there. Other people were working on projects, they were like, “What are you cooking up?”, and I’m like, “You don’t really want to eat this.”

Graham: Giant oar that you’re stirring the cauldron with.

Ashkahn: Yeah. It was also just an awesome place. They had every kitchen gadget you could imagine, and these crazy-

Graham: They call them lab gadgets, actually.

Ashkahn: Kitchen lab gadgets, and these huge burners, these stove tops with flames that were five or six times larger than the ones that come off of our stove at home. It was cool. It was a really fun day.

Graham: And we have a decent stove at home, too, just in case you thought that we have a wimpy stove.

Ashkahn: It doesn’t shy away from providing a big flame on its own. But this was serious. I had to turn it down.

Graham: So, yeah, that’s where we’re at right now with this stuff. We’ll have more coming out. Roy Vore promised us a nice blog post that he was going to write for Float Tank Solutions.

Ashkahn: Yeah, publicly announcing it should add some pressure.

Graham: Yeah, exactly. And if he doesn’t do it, he’s a big dumb-dumb head. You heard it here. That’s right, I’m calling you out, Roy Vore.

Graham: So, yeah, we have that to look forward to.

Ashkahn: And I think he said… So he’s going to speak at the float conference this year, and he was going to include this information in his talk.

Graham: I think he also said something about sending us $5,000.

Ashkahn: Yeah, he owes us that.

Graham: So, anyway, you have that to look forward to, too. We’ll definitely do another update on this stuff down the road, when we have a little more official science-y material to throw behind it.

Ashkahn: But I mean, boom, first time ever we know the water activity of float-tank solution. That’s pretty cool.

Graham: Anything else for the audience, as long as we’ve got them here, captive, unable to move?

Ashkahn: No, I feel like we probably shared more than we really needed to.

Graham: I know, we just got excited. We’re behind the mics again.

Ashkahn: It’s been a while.

Graham: It’s good to be back.

Ashkahn: Yeah, it’s nice.

Graham: Yeah, and we’ll see you occasionally in the future, as well.

Ashkahn: We don’t really have a way of ending these like we used to.

Graham: No, but I’m just-

Ashkahn: If you have a question, man, good luck with it, because we’ll be back at some point.

Graham: Actually, but really, if you do have anything that you want us to just yammer on about, send it in. We’re still taking ideas, “requests” I guess you could call them. We’re taking requests.

Ashkahn: Is there still a form up, or just email us?

Graham: Yeah, just yell really loud, we’ll hear it.

Ashkahn: If enough people think it , we actually will hear it in our heads.

Graham: I’m going to hop on my Segway and get out of here.

Ashkahn: Bye, guys.

Graham: Bye…

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