• Please visit and share your knowledge at our sister communities:
  • If you have not, please join our official Homebrewing Facebook Group!

    Homebrewing Facebook Group

The OFFICIAL Low Oxygen Brewing Thread, AKA lodo, lowdo, LOB

Homebrew Talk

Help Support Homebrew Talk:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Status
Not open for further replies.
I have copper too and still have good results attempting LODO. I don't use Brewtan B in the mash though but i do use SMB in the mash and sparge and Polyclar 730 plus after fermentation and as far as i can tell it too is an anti-oxidant.

You aren't doing LODO then. The threshold for oxidation is very very low with this method and you are exceeding it with fenton reactions. Due to the extremely low level of oxidation that is acceptable, this is not a linear process. You are exceeding 1ppm and therefore aren't doing LODO.
 
I have copper too and still have good results attempting LODO. I don't use Brewtan B in the mash though but i do use SMB in the mash and sparge and Polyclar 730 plus after fermentation and as far as i can tell it too is an anti-oxidant.

You aren't doing LODO then. The threshold for oxidation is very very low with this method and you are exceeding it with fenton reactions. Due to the extremely low level of oxidation that is acceptable, this is not a linear process. You are exceeding 1ppm and therefore aren't doing LODO.

While I agree that Fenton reactions should certainly be considered and that if copper is used that a metal chelating agent such as Brewtan B should be utilized, I disagree wholeheartedly with the remainder of your post.

This is not an “all or nothing” process. As good as the GBF “Helles” paper is, the one thing we are now stuck with is a stigma of the “all or nothing” mentality. If you are executing the mechanical and chemical exclusion methods on the hot side, then you are on the path. You may be sacrificing that flavor upstream but you can work on that. You can’t maintain a flavor you never preserved and preservation begins in the mash tun.

Chess: Keep doing what you are doing. It’s a marathon, not a sprint. You may see some impacts upstream with flavor longevity but nothing a SS chiller or some Brewtan B won’t help out with. You are on the right track.

I urge everyone to read ALL of the links that Beerery posted in the first post, especially these two:

http://www.lowoxygenbrewing.com/low-oxygen-methods/

and

http://www.lowoxygenbrewing.com/brewing-methods/low-oxygen-review/

The GBF Helles papers are a great resource but there is some information in there that needs to be updated and corrected. I would recommend against using it as a sole resource for the information about Low Oxygen brewing.
 
You aren't doing LODO then. The threshold for oxidation is very very low with this method and you are exceeding it with fenton reactions. Due to the extremely low level of oxidation that is acceptable, this is not a linear process. You are exceeding 1ppm and therefore aren't doing LODO.

I use a Therminator (copper brazed stainless) for chilling my strike water and a Hydra (which has a huge copper surface are) for chilling the boil and i still see significant flavor benefits, especially in regards to flavor longevity.

Maybe(?) not as good as an all stainless system, but the gains to be had from low oxygen mashing via pre-boiled water and chemical or biological scavenging, along with spunding on the cold side are well worth the efforts.
 
You aren't doing LODO then. The threshold for oxidation is very very low with this method and you are exceeding it with fenton reactions. Due to the extremely low level of oxidation that is acceptable, this is not a linear process. You are exceeding 1ppm and therefore aren't doing LODO.

I see. Actually I have a stainless steel heated mash tun, a stainless steel false bottom, stainless steel fittings and the only copper I have on it is a 3/4 bsp nut and a copper pipe thats about 12cm long. Also a copper wort chiller. Are these enough to exceed 1ppm oxygen ingress due to fenton reactions? As the learned gentlemen above have stated, its not an all or nothing proposition and having adopted the methodology as best I can with the ingredients and equipment that I have at my disposal I can honestly state that I have observed a marked improvement in the quality of the beers that I make. Remarkably so. If its not LODO then so be it but I still like it.
 
While I agree that Fenton reactions should certainly be considered and that if copper is used that a metal chelating agent such as Brewtan B should be utilized, I disagree wholeheartedly with the remainder of your post.

This is not an “all or nothing” process. As good as the GBF “Helles” paper is, the one thing we are now stuck with is a stigma of the “all or nothing” mentality. If you are executing the mechanical and chemical exclusion methods on the hot side, then you are on the path. You may be sacrificing that flavor upstream but you can work on that. You can’t maintain a flavor you never preserved and preservation begins in the mash tun.

Chess: Keep doing what you are doing. It’s a marathon, not a sprint. You may see some impacts upstream with flavor longevity but nothing a SS chiller or some Brewtan B won’t help out with. You are on the right track.

I urge everyone to read ALL of the links that Beerery posted in the first post, especially these two:

http://www.lowoxygenbrewing.com/low-oxygen-methods/

and

http://www.lowoxygenbrewing.com/brewing-methods/low-oxygen-review/

The GBF Helles papers are a great resource but there is some information in there that needs to be updated and corrected. I would recommend against using it as a sole resource for the information about Low Oxygen brewing.

you can disagree with me if you want, but my point is grounded in science, and the nice thing about science is its true whether you agree with it or not. This process involves keeping very sensitive malt polyphenols from getting oxidized. These compounds are oxidized at an incredibly low DO level. fenton reactions take your beer above that very low threshold. This isn't my opinion, this is science. If you have copper in your system and are doing nothing to mitigate its deleterious effects, you are oxidizing your beer above the threshold. End of story.
 
I see. Actually I have a stainless steel heated mash tun, a stainless steel false bottom, stainless steel fittings and the only copper I have on it is a 3/4 bsp nut and a copper pipe thats about 12cm long. Also a copper wort chiller. Are these enough to exceed 1ppm oxygen ingress due to fenton reactions? As the learned gentlemen above have stated, its not an all or nothing proposition and having adopted the methodology as best I can with the ingredients and equipment that I have at my disposal I can honestly state that I have observed a marked improvement in the quality of the beers that I make. Remarkably so. If its not LODO then so be it but I still like it.

the bastardization of all the research and work done by people prior to the homebrew scaling and dumbing down of Low oxygen brewing drives me nuts. The truth is, the threshold of DO is very low. This is one area where the pros have it better than us. Mash tun geometry, automation, more high tech oxygen stripping tech and precision engineering gve the pros an upper hand.

I cringe for Kunze when I hear concessions being made that render the entire process pointless.
 
I use a Therminator (copper brazed stainless) for chilling my strike water and a Hydra (which has a huge copper surface are) for chilling the boil and i still see significant flavor benefits, especially in regards to flavor longevity.

Maybe(?) not as good as an all stainless system, but the gains to be had from low oxygen mashing via pre-boiled water and chemical or biological scavenging, along with spunding on the cold side are well worth the efforts.

just...no. malt polyphenols that you are trying to preserve oxidize at such a low threshold will be gone. The suggestions made by the low oxygen proponents here are good, especially on the cold side. Better yeast and fermentation management, Homebrewers that were once siphoning their beer into an open keg are now doing closed transfers and spunding. Cold crashing with CO2 reservoirs instead or letting air get sucked back (although with proper technique fermenter cold crashing can be eliminated.) These things will make an already oxidized beer seem less oxidized, but low oxygen brewing involves, well low oxygen. The german "it" is real. Whether everyone can taste it is another story, but that much copper in your system is oxidizing your beers and you are losing the polyphenols we try so hard to keep.
 
you can disagree with me if you want, but my point is grounded in science, and the nice thing about science is its true whether you agree with it or not. This process involves keeping very sensitive malt polyphenols from getting oxidized. These compounds are oxidized at an incredibly low DO level. fenton reactions take your beer above that very low threshold. This isn't my opinion, this is science. If you have copper in your system and are doing nothing to mitigate its deleterious effects, you are oxidizing your beer above the threshold. End of story.

You're preaching to the choir! I'm pretty familiar with the process...;)

I don't think anyone will disagree with the science, especially not Beerery or I, but advocating for a stepwise approach is getting people interested in the methods.

Subsequent equipment modifications or the incorporation of some sort of gallotannin based compound like Brewtan B will help those with small amounts of copper in their systems. People are getting great results using their copper chillers and BTB.


You're not wrong in a technical sense but rather in the way you communicate it. They are plenty of people at the LOB forum, HBT and the AHA forum who worked their way up to all SS systems and follow the methods to a T. They wouldn't have gotten there without a phased approach. Say what you want about that but it's a big leap forward to communicating the ideas in a desirable way.

the bastardization of all the research and work done by people prior to the homebrew scaling and dumbing down of Low oxygen brewing drives me nuts. The truth is, the threshold of DO is very low. This is one area where the pros have it better than us. Mash tun geometry, automation, more high tech oxygen stripping tech and precision engineering gve the pros an upper hand.

I cringe for Kunze when I hear concessions being made that render the entire process pointless.

Being that I co-founded LOB.com with one of those people I find it hard to stomach the word bastardization. I'd say Low Oxygen brewing has been vastly expanded and improved by our contributions. You have to start somewhere. While I agree that many people start out with obvious flaws remaining in the way they execute the process, the fact is they are trying it and improving with every subsequent batch. I can't see anything wrong with that.

If you have any questions about the techniques just let us know.
 
You're preaching to the choir! I'm pretty familiar with the process...;)

I don't think anyone will disagree with the science, especially not Beerery or I, but advocating for a stepwise approach is getting people interested in the methods.

Subsequent equipment modifications or the incorporation of some sort of gallotannin based compound like Brewtan B will help those with small amounts of copper in their systems. People are getting great results using their copper chillers and BTB.

You're not wrong in a technical sense but rather in the way you communicate it. They are plenty of people at the LOB forum, HBT and the AHA forum who worked their way up to all SS systems and follow the methods to a T. They wouldn't have gotten there without a phased approach. Say what you want about that but it's a big leap forward to communicating the ideas in a desirable way.



Being that I co-founded LOB.com with one of those people I find it hard to stomach the word bastardization. I'd say Low Oxygen brewing has been vastly expanded and improved by our contributions. You have to start somewhere. While I agree that many people start out with obvious flaws remaining in the way they execute the process, the fact is they are trying it and improving with every subsequent batch. I can't see anything wrong with that.

I agree. It would be very hard for a lot of people to get new equipment or replace their current stuff all at once. While brewing with a cooper chiller may not be the best lodo practice, it gets people to try lodo with other parts of brewing until they can get all SS parts.

I'm just starting and will be using my cooper chiller. I don't have brewtan b either. Not the best situation but it is what I have to deal with for now. It will still be less oxygen than before. Maybe for those that can't go full out right away, we call it lower oxygen brewing.
 
You're preaching to the choir! I'm pretty familiar with the process...;)

I don't think anyone will disagree with the science, especially not Beerery or I, but advocating for a stepwise approach is getting people interested in the methods.

Subsequent equipment modifications or the incorporation of some sort of gallotannin based compound like Brewtan B will help those with small amounts of copper in their systems. People are getting great results using their copper chillers and BTB.


You're not wrong in a technical sense but rather in the way you communicate it. They are plenty of people at the LOB forum, HBT and the AHA forum who worked their way up to all SS systems and follow the methods to a T. They wouldn't have gotten there without a phased approach. Say what you want about that but it's a big leap forward to communicating the ideas in a desirable way.



Being that I co-founded LOB.com with one of those people I find it hard to stomach the word bastardization. I'd say Low Oxygen brewing has been vastly expanded and improved by our contributions. You have to start somewhere. While I agree that many people start out with obvious flaws remaining in the way they execute the process, the fact is they are trying it and improving with every subsequent batch. I can't see anything wrong with that.

If you have any questions about the techniques just let us know.

A step wise approach is fine, just don't kid yourself into thinking you are following a truly scientific approach or the teachings of Kunze or Narziss while doing it. If people need to make a hundred no Low oxygen batches while incorporating a step by step tiny change approach, then by all means, just don't kid yourself into thinking you haven't volatized the polyphenols we are all so desperately trying to keep.
I understand you and that other guy have put some time into a website and need to make this approachable to the average homebrewer, but by sacrificing the very specific and technical aspects of the brewing process to do that, you destroy it in the process. Here's the science and inescapable truth: Low oxygen brewing yields a different product that other methods, and for a homebrewer, you have a very very very small margin of error. Throwing 50 feet of copper into your beer, or having a 1 foot deep, half foot wide open mash with no mash cap or any number of other things I've hear people espouse to doing while still claiming to be doing low oxygen brewing is simply incorrect and a bastardization of all the work brewing scientists have done on this subject.
 
A step wise approach is fine, just don't kid yourself into thinking you are following a truly scientific approach or the teachings of Kunze or Narziss while doing it. If people need to make a hundred no Low oxygen batches while incorporating a step by step tiny change approach, then by all means, just don't kid yourself into thinking you haven't volatized the polyphenols we are all so desperately trying to keep.
I understand you and that other guy have put some time into a website and need to make this approachable to the average homebrewer, but by sacrificing the very specific and technical aspects of the brewing process to do that, you destroy it in the process. Here's the science and inescapable truth: Low oxygen brewing yields a different product that other methods, and for a homebrewer, you have a very very very small margin of error. Throwing 50 feet of copper into your beer, or having a 1 foot deep, half foot wide open mash with no mash cap or any number of other things I've hear people espouse to doing while still claiming to be doing low oxygen brewing is simply incorrect and a bastardization of all the work brewing scientists have done on this subject.
You would not be, by any chance, associated with that other site? :)
 
I agree. It would be very hard for a lot of people to get new equipment or replace their current stuff all at once. While brewing with a cooper chiller may not be the best lodo practice, it gets people to try lodo with other parts of brewing until they can get all SS parts.

I'm just starting and will be using my cooper chiller. I don't have brewtan b either. Not the best situation but it is what I have to deal with for now. It will still be less oxygen than before. Maybe for those that can't go full out right away, we call it lower oxygen brewing.

If it was easy, we'd all be making Bitburger. Copper chiller with no mitigation for its effects will preclude you from brewing low oxygen. This isn't me saying this, this is brewing science.
 
You would not be, by any chance, associated with that other site? :)

I have no site affiliation. Just passionate about beer and have studied and practiced this aspect of brewing and its VERY difficult to see the shortcuts, and to use a much maligned word, bastardization of the process to placate the homebrewing masses.
 
A step wise approach is fine, just don't kid yourself into thinking you are following a truly scientific approach or the teachings of Kunze or Narziss while doing it. If people need to make a hundred no Low oxygen batches while incorporating a step by step tiny change approach, then by all means, just don't kid yourself into thinking you haven't volatized the polyphenols we are all so desperately trying to keep.
I understand you and that other guy have put some time into a website and need to make this approachable to the average homebrewer, but by sacrificing the very specific and technical aspects of the brewing process to do that, you destroy it in the process. Here's the science and inescapable truth: Low oxygen brewing yields a different product that other methods, and for a homebrewer, you have a very very very small margin of error. Throwing 50 feet of copper into your beer, or having a 1 foot deep, half foot wide open mash with no mash cap or any number of other things I've hear people espouse to doing while still claiming to be doing low oxygen brewing is simply incorrect and a bastardization of all the work brewing scientists have done on this subject.

Ultimately we adhere strictly and fully to the tenants of Low Oxygen brewing (we being Beerery and I and a good number of regulars on our own forum). We blog about a great number of topics and always clearly state where there is an opportunity for departure from the generally accepted and acknowledged techniques. We also let people know what they may lose by deviating.

Advocating that people take a step-wise approach is a compromise we are willing to endure if it means that people try the method and report back results. Many people have stated that were it not for their initial shortcomings (and the subsequent advice they got from others on improving) they wouldn't be brewing such quality beer as they do now.

Believe me when I say this: We have a great respect for Kunze, Narziss, Fix, De Clerck, etc. I don't think anyone that deviates from the process feels they are disrespecting great brewing scientists by doing so. Many have an even greater admiration for them after they begin using the techniques. They are merely doing what they can with their time and equipment to try the process. Most find that after they taste Low Oxygen wort coming from the mash tun that they are more than willing to make improvements toward making that flavor last.

What has your experience with Low Oxygen brewing shown you? Do you have any insights that you'd like to share? We are always looking for opinions on the process and how people are making it work in their setup. What is your setup like? People are always looking for setup descriptions so that they can use it as a reference.

Please share!
 
I have no site affiliation. Just passionate about beer and have studied and practiced this aspect of brewing and its VERY difficult to see the shortcuts, and to use a much maligned word, bastardization of the process to placate the homebrewing masses.

Passion is where it's at. We just ask that everyone who wants to contribute to the thread do it respectfully. There are people trying the methods who understand some of the shortcomings in their own process and want to improve. We don't want to alienate a potential contributor.

We have a whole slew of people from many forums who are getting interested and excited about this. The best thing we can do is help those people along.

I like h22lude's idea of calling it "lower oxygen" brewing until fully converted!
 
If it was easy, we'd all be making Bitburger. Copper chiller with no mitigation for its effects will preclude you from brewing low oxygen. This isn't me saying this, this is brewing science.

I understand that. I'm not disagreeing with you. I'm saying a lot of people need to take steps to get to low oxygen brewing. Not everyone can afford to replace everything all at once. If cooper is the only thing keeping someone from brewing a true low oxygen beer, I'd say they are well on their way to low oxygen. This is why I made the last comment in my last post...call it lower oxygen brewing. If I change my process to low oxygen but still use a cooper chiller, my beers will still have less oxygen than they did before....lower oxygen.

Having a negative attitude (or at least coming off that way) will keep people away from these types of posts. I understand what you are trying to say but I think you need to realize that people need to take steps to get to the end result and by doing so they aren't disrespecting the scientists/brewers that helped pave the way for this.
 
Back on topic, I want to keep NaMeta use low. I also want to try Brewtan while I have my cooper chiller. I plan on using 10mg/l of NaMeta (.3g for my mash). This puts SO4 to 10 and Na to 2.5. How do I figure how much Brewtan B to use and does that affect anything in the water?
 
I understand that. I'm not disagreeing with you. I'm saying a lot of people need to take steps to get to low oxygen brewing. Not everyone can afford to replace everything all at once. If cooper is the only thing keeping someone from brewing a true low oxygen beer, I'd say they are well on their way to low oxygen. This is why I made the last comment in my last post...call it lower oxygen brewing. If I change my process to low oxygen but still use a cooper chiller, my beers will still have less oxygen than they did before....lower oxygen.

Having a negative attitude (or at least coming off that way) will keep people away from these types of posts. I understand what you are trying to say but I think you need to realize that people need to take steps to get to the end result and by doing so they aren't disrespecting the scientists/brewers that helped pave the way for this.

this is true, but the polyphenols that give these beers the elusive taste we're in search of will not be present and you certainly wont be brewing to the specs of the very brewing scientists that brought forth this method of brewing.
 
Back on top, I want to keep NaMeta use low. I also want to try Brewtan while I have my cooper chiller. I plan on using 10mg/l of NaMeta (.3g for my mash). This puts SO4 to 10 and Na to 2.5. How do I figure how much Brewtan B to use and does that affect anything in the water?

What system changes have you made? We recommend 20-30 ppm to start depending on what your equipment upgrades have been.

BTB doesn't affect water composition or pH like Meta does. The recommended values listed on Wyeast's site for the mash is 0.25 g/gal.
 
this is true, but the polyphenols that give these beers the elusive taste we're in search of will not be present and you certainly wont be brewing to the specs of the very brewing scientists that brought forth this method of brewing.

There are plenty of people tasting the characteristic Low Oxygen malt flavor coming out of the mash tun. Whether it persists is the question.

That's what people are working on. People using copper and Brewtan B are experiencing persistent Low Oxygen malt flavor. It's a learning process for sure and those who pick it up are eager to preserve the flavor from the tun into the finished and packaged beer.
 
Ultimately we adhere strictly and fully to the tenants of Low Oxygen brewing (we being Beerery and I and a good number of regulars on our own forum). We blog about a great number of topics and always clearly state where there is an opportunity for departure from the generally accepted and acknowledged techniques. We also let people know what they may lose by deviating.

Advocating that people take a step-wise approach is a compromise we are willing to endure if it means that people try the method and report back results. Many people have stated that were it not for their initial shortcomings (and the subsequent advice they got from others on improving) they wouldn't be brewing such quality beer as they do now.

Believe me when I say this: We have a great respect for Kunze, Narziss, Fix, De Clerck, etc. I don't think anyone that deviates from the process feels they are disrespecting great brewing scientists by doing so. Many have an even greater admiration for them after they begin using the techniques. They are merely doing what they can with their time and equipment to try the process. Most find that after they taste Low Oxygen wort coming from the mash tun that they are more than willing to make improvements toward making that flavor last.

What has your experience with Low Oxygen brewing shown you? Do you have any insights that you'd like to share? We are always looking for opinions on the process and how people are making it work in their setup. What is your setup like? People are always looking for setup descriptions so that they can use it as a reference.

Please share!

to the first highlighted text, this method does not afford "departure". This is a precise scientific method of brewing, and at the homebrewing level there is even less of a margin of error that allows for "departure".

to the second, your compromise is destroying the very thing you're after. Science doesn't compromise. You are consenting to let new brewers volatize the very compounds that you are purporting to seek. You are throwing the baby out with the bathwater so to speak.

to the third, claiming to have great respect for brewing scientists, and quoting them at every turn, then admittedly allowing deviation from their scientific methods is disingenuous at best. You can respect them by following their discoveries and scientific methods and not compromise their work to placate the homebrewing masses.


The truth is, trying this approach with traditional homebrewing equipment (copper, poor or non existent trub separation, poor grain crush, the list goes on and on) is not possible. If brewers want to do this, they need to concede to the science that already exists and do it right.

Heres a very simple analogy: I want to make a yeast starter, but I only have boiling water available, do I concede and compromise to throw my yeast into boiling water because my limitations dictate I do so? No, of course not, in my quest for what I'm after (more yeast) I destroy the very thing I'm hoping to accomplish.
 
to the first highlighted text, this method does not afford "departure". This is a precise scientific method of brewing, and at the homebrewing level there is even less of a margin of error that allows for "departure".

to the second, your compromise is destroying the very thing you're after. Science doesn't compromise. You are consenting to let new brewers volatize the very compounds that you are purporting to seek. You are throwing the baby out with the bathwater so to speak.

to the third, claiming to have great respect for brewing scientists, and quoting them at every turn, then admittedly allowing deviation from their scientific methods is disingenuous at best. You can respect them by following their discoveries and scientific methods and not compromise their work to placate the homebrewing masses.


The truth is, trying this approach with traditional homebrewing equipment (copper, poor or non existent trub separation, poor grain crush, the list goes on and on) is not possible. If brewers want to do this, they need to concede to the science that already exists and do it right.

Heres a very simple analogy: I want to make a yeast starter, but I only have boiling water available, do I concede and compromise to throw my yeast into boiling water because my limitations dictate I do so? No, of course not, in my quest for what I'm after (more yeast) I destroy the very thing I'm hoping to accomplish.

You seem passionate. That leads me to believe you have tried the process. That's a good thing. We (the royal we) would love to hear about your experiences using low oxygen methods.

You also seem to be itching for a fight, which is alright too. That comes with passion. Just don't expect much constructive conversation.

Again, I hope you'll share your thoughts on your process, experiences and equipment choices here. We would love to hear how you've implemented the process and would love to see your equipment.

Our thoughts and ideas are documented here if you are interested in reading:

http://www.lowoxygenbrewing.com/
 
I have shared my thoughts. If people want to do low oxygen brewing, then read the classic texts, get the proper tools and equipment to do so and do it.
 
I have shared my thoughts. If people want to do low oxygen brewing, then read the classic texts, get the proper tools and equipment to do so and do it.

I meant share your thoughts on your process. You seem to have adopted the technique and must surely have some insights on how you integrated them into your setup and process.
 
And stop compromising and calling is low oxygen. It simply isn't. When oxidize your beer, it is no longer low oxygen. this isn't a difficult concept to understand.
 
And stop compromising and calling is low oxygen. It simply isn't. When oxidize your beer, it is no longer low oxygen. this isn't a difficult concept to understand.

So your main beef is with people using copper without a chelating agent such as Brewtan B/gallotannin? Is that correct?

They represent a small subsection of the people trying it and are more than willing to rectify it as soon as they are able.
 
I meant share your thoughts on your process. You seem to have adopted the technique and must surely have some insights on how you integrated them into your setup and process.

sure. Dial in your cold side completely. closed transfers, 100% flushed kegs, spunding and proper fermentation management. Pitching rates, temps and most of what homebrewers consider good practice are out the window with this. Eliminate copper, develop a way to preboil and chill to pitching temps rapidly. mind your ph. Stop crushing your grain to flour. Small adjustable SS wine fermenters with adjustable fermentation caps make an easy mash tun with a proper fitting mash cap. Get your water chemistry right. To call commercially avaialbe co2 of dubious purity is an understatement. The truth is, most of it is impure as hell and will oxidize your beer. Theres plenty more I'm just thinking on the fly here.
 
Status
Not open for further replies.
Back
Top