oxygen permeability of plastic

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MachineShopBrewing

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I don't know why the hell I do this kind of stuff and stir up the usual HBT flamers, but here goes anyway. I read an article that I thought was interesting and I thought I would share it.

I want to make a couple of things clear from the get-go:

1. Yes, lots of people ferment in buckets and do just fine.
2. Yes, lots of people ferment in buckets and win bjcp comps.
3. Yes, you ferment in a bucket and your beer is awesome.
4. If you like your beer and you ferment in a bucket, great. Soldier on.
5. If you ferment in a bucket and notice some premature staling, then this thread is for you.
6. Yes, I am sure this topic has been beaten to death, but what the hell. This forum is for discussion, isn't it?
7. If you are just going to chime in to flame, then don't bother. You don't add anything to the conversation.
8. If you are just going to chime in to say that I don't know what I am talking about because I am not a premium supporter, then don't bother.
9. If you are only going to chime in to say that "we have beat this topic to death and we aren't discussing it anymore" than don't bother. Only those who want to discuss it, should discuss it. If you don't want to, then don't. It just adds a lot of BS posts for the rest of us to weed through.
10. If you are going to pick and choose which lines to read in this post rather than reading the whole post for what it is(just sharing information) in order to create a straw man which you can then proceed to knock over and show your superior intellect, then don't bother.

Now that the required HBT controversial topic disclaimers are out of the way....

http://www.foodinnova.com/foodInnova/docu2/322.pdf

I am sure I'm not the only one who has seen this article on oxygen permeability for plastic containers used for fermented beverages. According to the research that they did for this paper, they found that in a 190L HDPE tank, they were able to record 2.15mg/L of dissolved oxygen per month making it through the walls of the container.

Now a 190L container has much more surface area than a ~24L(~6.5 gallon). Just converting that down linearly would equate to .2688 mg/L of dissolved oxygen making it through the bucket per month into the beer. Now there may be some variables that alter this number slightly, but it should be close enough for discussion's sake. If my math is correct, this would equate to 268.8 ppb of dissolved oxygen per month absorbed into the beer for every month of storage. In a personal conversation with Dave Berg, head brewer at Schell's brewing, he stated that you want under 50 ppb of dissolved oxygen to help prevent premature beer staling.

I know that the yeast may take up some of this oxygen even after fermentation is complete, but I suspect that they don't take up all of it.

I have a very low taste threshold for oxidation in my beers, and I was noticing some premature oxidation character in my beers while I was using plastic buckets. Sure, I won some comps with those beers, but maybe my taste threshold is lower than some people for oxidation. I have since switched to glass and that oxidation character has disappeared.

As always YMMV, and do whatever you think is good for you. I just wanted to share this information.



Let the flames begin...:rockin:
 
I know that the wine industry has several options, and among them are HDPE tanks specifically designed for oxygen permeability.

Their material and construction probably differs greatly from the HDPE buckets most homebrewers use.

The article you present specifically mentions, "...they may have a controlled
permeability, which makes their use more attractive for the cellars."


Further: "In this work it has been analyzed the Oxygen Transfer Rate (OTR) in a controlled permeability 190L HDPE wine tank (Flextank, Australia) by an analysis of the uniformity of the dissolved oxygen (DO) distribution. Non-invasive and non-oxygen consume optoluminescence technology has been used for the analysis of the spatial distribution of the DO concentration, as it is essential to know and control the process. It has been done the control of the same red wine aged in HDPE tanks and in barrels simultaneously, to analyze and compare the differences between the two aging systems."

So I wonder if using this article as a basis for understanding the O2 permeability of bucket fermenters is really appropriate?
 
Where I work we have a tolerance of 300ppb in the bottle (force carbed, no yeast), we put an 8 month shelf life on our core beers.

We'll make sure what's in the tank is under 50ppb (often under 20), but the dodgy Italian bottling machine likes to add oxygen. Last week the run of 8000 bottles I did was averaging 130ppb (I measure every half hour).

We use stainless tanks obviously, but it just goes to show how easy it is to introduce nasty stinking oxygen down the line.
 
+1 to homercidal's comment about the container used in the study not being comparable to the container used in homebrewing.

I also wanted to comment on this:
I have a very low taste threshold for oxidation in my beers, and I was noticing some premature oxidation character in my beers while I was using plastic buckets. Sure, I won some comps with those beers, but maybe my taste threshold is lower than some people for oxidation. I have since switched to glass and that oxidation character has disappeared.

I wonder if you could pick up the oxidation if you were blinded to the beers that came out of the buckets versus those that came out of the glass. My point being is that is tough to not taste something once you have a bias in mind.
 
it takes a while for oxidation, at these low levels, to be detectable. i can go through a 5 gallon batch faster than any oxidation can so i don't mind if a bit of oxygen gets in my beer, if it even is getting in through the plastic. even if i did use glass or steel to ferment in i'm sure i'm getting some O2 in the beer down the line somewhere, so is everyone else. it's like trying to run between the drops during a rainstorm, you can either give in to it now or later.
 
+1 to homercidal's comment about the container used in the study not being comparable to the container used in homebrewing.

I also wanted to comment on this:


I wonder if you could pick up the oxidation if you were blinded to the beers that came out of the buckets versus those that came out of the glass. My point being is that is tough to not taste something once you have a bias in mind.

exactly.
 
Flextanks design is SUPPOSED to allow more O2. That is their selling point. I'm not arguing that HDPE is as good as glass, or even that you can taste the difference. I just think more information about your claims is needed.

Here is a chart showing the O2 permeability of various types of wine containers, from Flextank's Own brochure:

hdpe_o2_compare.jpg


Note that racking twice allows more O2 than the HDPE tanks that are not designed for O2 permeability.

It's well known that HDPE is far ahead of any other food grade plastic, except PET, for Oxygen Permeability.
 
Oh, and by using this chart we can assume a 6X greater O2 permeability over their previous HDPE vessel (which may or may not share permeability with the HDPE buckets we use...)

And by using your own number or 268.8 and dividing by 6 we get 44.8 ppb, which is comfortably less than the 50 ppb that Dave Berg from Schell's states is wanted to prevent staling.
 
Their material and construction probably differs greatly from the HDPE buckets most homebrewers use.

This could be, as they don't really specify in the article. But, I am familiar with plastics and HDPE is pretty much the same across the board. Thickness may play a part in moving that number slightly, but permeability is permeability.

Here is another paper talking about the gas permeability of HDPE among other things http://www.plastics.org.nz/documents/ronz-hdpe-fact-sheet.pdf


Where I work we have a tolerance of 300ppb in the bottle (force carbed, no yeast), we put an 8 month shelf life on our core beers.

Suppose you had 100-200ppb and the 8 month shelf life on the bottle, at what point would you say that a lighter or hoppy beer would peak and start heading south when kept around 40F (~4.5C)? In your experience.


I wonder if you could pick up the oxidation if you were blinded to the beers that came out of the buckets versus those that came out of the glass. My point being is that is tough to not taste something once you have a bias in mind.

I am confident that I could pick out the oxidation if it was indeed present. I can pick it up in commercial beers very easily if they have it. I actually didn't have a bias when I first started tasting it. I was tasting the oxidation first and then tracked it down to the buckets. I always keg with flushed kegs and I even flush my auto-siphon with CO2 when racking to the keg, so the pickup there should have been negligible.
 
Flextanks design is SUPPOSED to allow more O2. That is their selling point. I'm not arguing that HDPE is as good as glass, or even that you can taste the difference. I just think more information about your claims is needed.

Here is a chart showing the O2 permeability of various types of wine containers, from Flextank's Own brochure:

Those are all good and valid points. Maybe I should try to reach out to the bucket manufacturers to see if they have any information. I suspect that the buckets are made as cheaply as possible without regard to O2 permeability.


EDIT: I sent an email to LD Carlson trying to reach the manufacturer of the "ale pail" buckets to find some more information.


EDIT EDIT: I also sent an email to John Smeaton, PhD, who is the technical director for Flextanks to ask what his thoughts are on the subject. I will report if and when I get some more information.
 
Ooops, I made a mistake. I used the number for the 2X wine transfer. I meant to use the HDPE Storage Tank.

So, recalculating...

That's about a 15 x difference, so 268.8 divided by 15 equals about 18 ppb...

Of course you'll also have to factor in the amount of O2 that you'd get by racking into the glass carboy (which, if you judge by the numbers given here, *could* be fairly significant, depending on your method and care).
 
I think you'll get more O2 in a smaller vessel, not less. Based on the surface area of the container in relation to the volume it contains. A 23 litre bucket with a radius of around 13 cm has about 170 square cm of surface area for every litre of beer. A scaled up version of that bucket holding 190 litres would have around 90 square cm of surface area for each litre of beer.

So wouldn't you get more O2 in a smaller vessel? As you scale up any 3d object, it's volume increases at a greater rate than it's surface area.

I love this topic. May it never die.
 
I think it would also be worthwhile to know the oxygen permeability of the blue HDPE 55 gallon storage barrels, and smaller 15 gallons barrels that they ship foodstuffs in, including LME.
 
MachineShopBrewing said:
Suppose you had 100-200ppb and the 8 month shelf life on the bottle, at what point would you say that a lighter or hoppy beer would peak and start heading south when kept around 40F (~4.5C)? In your experience.

I tried some black IPA that we'd stashed at 70-75f room temp for 9 months (QA sample), it wasn't oxidised but the hop character had muted as you'd expect.

On stronger, darker beers we put longer life on (7.7% RIS gets two years). We put some double IPA (7.4%, 8 month shelf life) in a bath at 140f for a couple of weeks to simulate two years aging, it wasn't very nice, lost hop character and I think there were signs of oxidation there.

As for cellar or fridge temps? Not sure, we haven't tested that.
 
I am confident that I could pick out the oxidation if it was indeed present. I can pick it up in commercial beers very easily if they have it. I actually didn't have a bias when I first started tasting it. I was tasting the oxidation first and then tracked it down to the buckets. I always keg with flushed kegs and I even flush my auto-siphon with CO2 when racking to the keg, so the pickup there should have been negligible.
What was your typical time in the bucket?
 
What was your typical time in the bucket?

2-4 weeks typically with a week of that being cold crash. A couple may have been 5-6 weeks when I was being lazy.

Ooops, I made a mistake. I used the number for the 2X wine transfer. I meant to use the HDPE Storage Tank.

So, recalculating...

That's about a 15 x difference, so 268.8 divided by 15 equals about 18 ppb...

Of course you'll also have to factor in the amount of O2 that you'd get by racking into the glass carboy (which, if you judge by the numbers given here, *could* be fairly significant, depending on your method and care).

I am not following what you are explaining here. Where are you pulling the 15 from?
 
2-4 weeks typically with a week of that being cold crash. A couple may have been 5-6 weeks when I was being lazy.
Was there a time lag when you noticed the effects or was it immediate. Have others noticed it in your beers? Just curious because people have different taste thresholds. I was brewing with a friend on Sunday and I had three different aged Scottish ales that we sampled in succession. He picked up something in the last one that I had forgotten I had put in which was just a very slight modification of the recipe. I had thought it made no difference. Well, to me it didn't I guess. :D
 
Was there a time lag when you noticed the effects or was it immediate. Have others noticed it in your beers? Just curious because people have different taste thresholds. I was brewing with a friend on Sunday and I had three different aged Scottish ales that we sampled in succession. He picked up something in the last one that I had forgotten I had put in which was just a very slight modification of the recipe. I had thought it made no difference. Well, to me it didn't I guess

Its hard to say now. I know with my hoppy beers I picked it up sooner than with darker/non hoppy beers. I have since found out that hoppy beers oxidize quicker than non hoppy beers, but I don't recall the source for that information.

By sooner, I am thinking around the 4-5 week in the keg mark? Its been a while, so some of it is lost to the fog of time and ethanol laced memory.
 
This article doesn't seem relevant to plastic beer fermenters. The point seems to be the controlled, PURPOSEFUL, introduction of oxygen.
My thinking in recently using buckets for primary fermentation, which allows me to produce batches just a hair under 7 gallons with the same gear as I use to make 5 gallon batches, is that the outward pressure of the denser CO2 should counteract the inward migration of oxygen. Maybe this wouldn't apply to a batch kept in a bucket for several months, or maybe I'm just wrong, but I'm chancing it for now.
 
This article doesn't seem relevant to plastic beer fermenters. The point seems to be the controlled, PURPOSEFUL, introduction of oxygen.

I think the article was more showing how much oxygen permeated through their storage tanks regardless of how or why. True, they are selling a product to people who would want the oxygen, but the research is still valid. I am still waiting to hear from the manufacturer if these numbers are similar across the board.
 
Its hard to say now. I know with my hoppy beers I picked it up sooner than with darker/non hoppy beers. I have since found out that hoppy beers oxidize quicker than non hoppy beers, but I don't recall the source for that information.

Hoppy beers certainly oxidize faster than non-hoppy beers. The iso-alpha acids break down over time and free up oxygen, which causes staling. Dr. Charlie Bamforth did a lecture about this and other related topics at this past year's NHC. Even if brewers could eliminate 100% of the oxygen introduced during transfers, packaging, etc. (which they spend millions on) they are SOL because the iso-alpha acids still break down over time.
 
I have been trying to reconcile the numbers on Raj's site WRT HDPE bucket oxygen permeation. He lists 220 cc/L per year of O2. Unless my math is wrong, that is 220,000,000 ppb per year? Something doesn't sound right. Now not all of that will be dissolved I am sure, but something has to be wrong in my math.
If cc=ml then 220 cc/L should equal 220ml/L which is a 220/1000 ratio?

Raj's site-http://www2.parc.com/emdl/members/apte/flemishredale.shtml
 
I think the article was more showing how much oxygen permeated through their storage tanks regardless of how or why. True, they are selling a product to people who would want the oxygen, but the research is still valid. I am still waiting to hear from the manufacturer if these numbers are similar across the board.

No doubt the research is valid, the question is if its applicable. The assumption here is that HDPE is HDPE is HDPE. I don't know if it is or not, but the whole selling point of this "breathable HDPE" for the wine-maker is that it isn't. That you need to buy their product, and not any ol' HDPE container.
 
I am not following what you are explaining here. Where are you pulling the 15 from?


My original comparison was based on the old HDPE container showing 5 on the chart, compared to the "new" container being about 30 (The container you listed in your original post.

The difference between them was 6.

But then I realized I was looking at the wrong container on the chart. The old HDPE container had a value of about 2. So the there is a 15 times difference between the value of 30 for the "new" container and the old HDPE container.


Many other sites I have looked at show HDPE as having a .03 (long line of scientific numbers afterwards) compared to about .003 for PET. All of the other plastics showed as being 1.0 or higher. Since I don't know what that long line of scientific numbers actually equates to, I can't say exactly how much O2 if expected in a month long fermentation. I can only see the relative values.

So PET is about 10X better at blocking O2 as HDPE, and HDPE is at least 10X better than pretty much any other plastic.

It would be interesting to read if someone with the proper equipment could do some tests between the different containers using standard homebrewer methods and report the O2 levels in each. Until then, we only have manufacturers claims and speculation to go on.
 
It would be interesting to read if someone with the proper equipment could do some tests between the different containers using standard homebrewer methods and report the O2 levels in each. Until then, we only have manufacturers claims and speculation to go on.

It is in my plans someday to have a dissolved oxygen meter. When that day comes, I will devise some kind of experiment to figure out how much gets through.
 
I think what we need to think about here is not so much whether glass is a better O2 barrier (we all know it is), but whether a bucket is going to allow enough O2 into the beer to cause a noticeable difference in taste, all other things remaining the same.

Using a bucket as a primary should work as well as nearly any other container, for the simple fact that the yeast are producing CO2 at a rate large enough to force any O2 out the airlock, plus they are using O2 from the beer during the reproduction stage.

So in theory we can assume that once fermentation has started, the amount of O2 in the primary is negligible.

Now, if we use the primary only right through to packaging, there should be hardly any amount of O2 introduced into the beer except the very tiny amount that might permeate through the bucket walls.

Racking, however, now causes that headspace filled with CO2 to be left behind, and a new headspace, now filled with O2 containing air, to come in contact with the beer. However, it's a very short amount of time and the headspace is minimized in the bottle, and practically eliminated in a keg.

However if we use a secondary, either bucket or carboy, we leave the CO2 protection and introduce air to the beer while racking. If we don't purge the secondary with CO2, then the beer is also in long-term contact with O2. The amount depends on the amount of headspace. In a 5 gallon carboy, it might not be much. In a bucket, it's going to be a very substantial surface area and a large enough volume of air.

I personally don't mind doing a longer than average primary if my life necessitates it. And if I used a secondary, say for a RIS or Barleywine, what have you, I would not use a bucket. Regardless of how well the HDPE protects the beer from permeable O2, there is simply too much surface are in contact with a large volume of air.

If I could not get a carboy filled full enough to limit these things, then purging with some CO2 would be necessary.

My point is that the amount of O2 that can permeate the walls of a bucket are likely a very small fraction of the amount of O2 that can be introduced by racking. That's my theory anyway.
 
I think what we need to think about here is not so much whether glass is a better O2 barrier (we all know it is), but whether a bucket is going to allow enough O2 into the beer to cause a noticeable difference in taste, all other things remaining the same.

Using a bucket as a primary should work as well as nearly any other container, for the simple fact that the yeast are producing CO2 at a rate large enough to force any O2 out the airlock, plus they are using O2 from the beer during the reproduction stage.

So in theory we can assume that once fermentation has started, the amount of O2 in the primary is negligible.

Now, if we use the primary only right through to packaging, there should be hardly any amount of O2 introduced into the beer except the very tiny amount that might permeate through the bucket walls.

Racking, however, now causes that headspace filled with CO2 to be left behind, and a new headspace, now filled with O2 containing air, to come in contact with the beer. However, it's a very short amount of time and the headspace is minimized in the bottle, and practically eliminated in a keg.

However if we use a secondary, either bucket or carboy, we leave the CO2 protection and introduce air to the beer while racking. If we don't purge the secondary with CO2, then the beer is also in long-term contact with O2. The amount depends on the amount of headspace. In a 5 gallon carboy, it might not be much. In a bucket, it's going to be a very substantial surface area and a large enough volume of air.

I personally don't mind doing a longer than average primary if my life necessitates it. And if I used a secondary, say for a RIS or Barleywine, what have you, I would not use a bucket. Regardless of how well the HDPE protects the beer from permeable O2, there is simply too much surface are in contact with a large volume of air.

If I could not get a carboy filled full enough to limit these things, then purging with some CO2 would be necessary.

My point is that the amount of O2 that can permeate the walls of a bucket are likely a very small fraction of the amount of O2 that can be introduced by racking. That's my theory anyway.

well put.
 
Homer-

Yeah, you probably have it correct.

I think what we need to think about here is not so much whether glass is a better O2 barrier (we all know it is), but whether a bucket is going to allow enough O2 into the beer to cause a noticeable difference in taste, all other things remaining the same.

That is the key line right there. That is what I am interested in, although I use glass exclusively now. It would be nice to have hard evidence on exactly how much O2 would get dissolved into your finished beer, say, with a 4 week sit in the primary vessel. Would you be over the threshold that would cause premature staling? I think the only way to truly know would be to actually test the dissolved oxygen level at various points throughout fermentation and chart it out.
 
I have to say, I am surprised that this thread didn't get nailed by a bunch of flamers. I guess the disclaimer at the beginning worked, although I thought that it may rile them up as much as deter them.

:ban::mug:
 
I was able to get gas permeability information from the Ale Pail manufacturer.

This is the chart that they gave me:

GAS RATE(cc/mil/24hrs/100in^2)

CO2 345
Ethane 236
Hydrogen 321
Natural Gas 113
Oxygen 111
Freon 12 95
Helium 247
Nitrogen 53
Sulfur Dioxide 306

I have no idea how to relate cc/mil/24hrs/100in^2 into ppb or ppm, so I am hoping you chemistry guys can help me out there.
 
The numbers arrive and the thread dies?

To make those numbers usable you would have to determine the surface area of an ale pail. https://www.homebrewtalk.com/f11/ale-pail-dimensions-72525/ Let’s assume it is actually just a cylinder with a diameter of 11 inches and a height of 17.5. Which is 795 In^2. That means that we need to multiply the numbers supplied by 7.95, so 882 ml of oxygen every 24 hours… that doesn’t sound good. From there you would need to figure out how much oxygen that is compared to how much beer is in the fermentor.

As someone else said, the smaller the fermentor is the more oxygen it will let in because of the higher surface to volume ratio.

My bigger concern with buckets has always been the seal. If anyone hasn’t seen it Better Bottle did an oxygen permeability study on airlocks and bungs: http://www.better-bottle.com/pdf/Closures_Oxygen_Passage_Study.pdf
 
Supposing you would like to bulk condition your beer in a plastic food grade bucket with lid from the local HB store, could you not glue a layer of Mylar Space Blanket around bucket, lid, and bottom of bucket... that way even though the plastic container is not strictly oxygen impermeable, the oxygen will never touch the outsides of the container because of the space blanket. If space blankets can work as a barrier against hydrogen and helium, then by all rights it should stop oxygen too no? Or is the oxygen permeability of these buckets negligible anyway for long term beer conditioning? Just a thought....

Dom
 
However if we use a secondary, either bucket or carboy, we leave the CO2 protection and introduce air to the beer while racking. If we don't purge the secondary with CO2, then the beer is also in long-term contact with O2. The amount depends on the amount of headspace. In a 5 gallon carboy, it might not be much. In a bucket, it's going to be a very substantial surface area and a large enough volume of air.

But even then, the mere act of moving the beer will release some dissolved co2 left over from fermentation, so you're going to have at least a thin protective layer in the fermenter after racking. The O2 introduction happens more in the transfer process.
 
But even then, the mere act of moving the beer will release some dissolved co2 left over from fermentation, so you're going to have at least a thin protective layer in the fermenter after racking. The O2 introduction happens more in the transfer process.

I often add a tiny amount of table sugar (less than I use to carbonate) when racking to make this thin layer a little thicker. I can't tell you it works, but I'm pretty sure it does no harm.
 
My thinking in recently using buckets for primary fermentation, which allows me to produce batches just a hair under 7 gallons with the same gear as I use to make 5 gallon batches, is that the outward pressure of the denser CO2 should counteract the inward migration of oxygen. Maybe this wouldn't apply to a batch kept in a bucket for several months, or maybe I'm just wrong, but I'm chancing it for now.

But even then, the mere act of moving the beer will release some dissolved co2 left over from fermentation, so you're going to have at least a thin protective layer in the fermenter after racking. The O2 introduction happens more in the transfer process.

I guess I'm a little late in joining this thread, but I thought this might be useful...

Unfortunately, neither the pressure of the CO2 in the beer nor the thin layer of CO2 on top would keep O2 out. Any O2 in contact with the CO2 will diffuse into the CO2, and the CO2 will likewise diffuse into the O2 until they are completely, evenly mixed. This is, I believe, Henry's law relating to partial gas pressures.

As an example, the partial pressure of CO2 in normal air (the amount of CO2 contributes only a small fraction of a percent of the pressure because the amount of CO2 is so small) is significantly lower than the partial pressure of the CO2 from the beer (presumably close to 100 percent). On the flip side, the partial pressure from the O2 in the air (somewhere around 21 percent) is much higher than the partial pressure of the O2 from the beer (presumably close to 0 percent.) The result is that both gasses (CO2 and O2) will move from their areas of higher pressure to their areas of lower pressure.

This is exactly why a freshly opened beer (or soda) will eventually go flat and stale: most of the CO2 will escape out and O2 will get in and dissolve.
 
Good job explaining partial pressure and equilibrium. Just don’t expect anyone to believe you. It’s sounds wacky that oxygen could be coming in while carbon dioxide is going out.

I’m not a chemist, but I did pass organic. Here’s the part I have trouble with; it’s the timing. Gordon Fix said the gases in the headspace would stratify before diffusing. So given sufficient volume of CO2 we should be pushing most of the O2 out the airlock. I wonder what sort of volume that would be. Is there enough in secondary?

Diffusion into the wort would be a lot slower, so going back to oldsock’s calculation, we should take the surface area of the bucket for the part above the wort and then multiply the rest by some tiny fudge factor.

Any chem engineers out there that can help us out?
 
A bit off topic, but curious if oxygen permeability is a moot point for folks who cold crash. I know a lot of folks do it and it always made me think that be the easiest way to introduce oxygen other than bad racking.
 
Now this thread is giving me 2nd thoughts about conditioning my RIS in a hdpe jerry can for 6 mths as I didnt want to hold up a keg for that amount of time.

I was planning to fill the beer into the jerry can and purge that small little headspace with CO2 and put it in the fridge for 6 mths.

hmmm
 
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