# FlexTank instead of oak barrel...really interesting



## geek

I saw this link posted by manvswine in a different thread and found it very interesting..!!

Not sure if already posted someewhere so I figured it may good to post here:

http://www.flextankusa.com/index.php


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## ibglowin

I think flextanks are great and they definitley have a purpose in the winery, esp with white wines. But they can in no way replace a barrel for a red wine!
From the flextank website:

*The “Angels Share” is retained – no losses and no routine topping required.*

That right there tells you you have NO micro-oxidation going on as well as NO Concentration through evaporation via the loss to the Angels.

That said you can buy (a very expensive) Micro-oxidation delivery system to add on you a flextank but you still wont have the concentration effect.


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## grapeman

Mike the tanks do allow for micro-oxidation, but not concentration. According to their website:

*How does oxygen get into the wine?*
The tank itself is permeable to oxygen. The actual permeability required is engineered by attention to resin selection and blend, surface area to volume ratio and wall thickness. The maturation range of Flextanks is designed to have a similar oxygen permeation rate to the typical second year wine barrel when used at a nominal cellar temperature of 55F. Oxygen is driven across the tank wall by the partial pressure differential between the wine and the atmosphere. Upon permeating into the wine the oxygen is used up by the complex chemical changes that occur during maturation. 

I have seen somewhere online a chart comparing the oxygen permeability, but short of looking it up right now I don't have it at hand.
OK here it is


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## ibglowin

I was just reading that on their website. That is one heck of a claim……. That Polyethylene or Polypropylene whichever they are using has the same permeability as a wooden oak barrel.

If that is true then SO2 levels would be dropping like a rock when you use them just as they do with a barrel.

Is that what you see Rich? How does your SO2 levels hold up in a Flextank?


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## tonyt

So you get the oxygenation of a barrel but not the concentration. Both seem important to me as a home winemaker but a commercial winery making bulk wine would love to keep the angel share for themselves.


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## ibglowin

I still am not convinced they will oxidize at the same rate as a barrel. Need to see a comparative study! LOL I do know you can install an OxBox


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## grapeman

The S02 levels just need monitoring periodically and replacing as need be. It is just a maintenance operation. I find with my use it isn't much different than any other storage, but then the pH tends to be lower than with vinifera grapes.


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## GreginND

ibglowin said:


> If that is true then SO2 levels would be dropping like a rock when you use them just as they do with a barrel.



According to the studies on this page (http://www.flextank.com.au/trials-aus.htm), SO2 levels in flex tanks drop at the same rate as oak barrels.

_A 2006 Shiraz, after malo-lactic fermentation, was added to the following vessels:

3 x new American oak hogsheads
2 x 1000 Litre Flextanks, each containing one 'Flextank 8 QP' modular oak stave pack
3 x 2100 Litre Flextanks, each containing two 'Flextank 8 QP' modular oak stave packs

All vessels were kept in the same storage area (same temperature and humidity) for the eleven months duration of the trial. The intention of the trial was to monitor relative changes in various chemical parameters for the wines stored in the different vessels._







_Free sulfur dioxide concentration (mg/litre) in 2100 litre Flextanks (BP01, BP02, BP03), 1000 litre Flextanks (BP05, BP06)
and new American oak hogsheads over 5 months.

The free sulfur dioxide concentrations were essentially the same in all storage vessels after the 11 month maturation period. Importantly, the rate of free sulfur dioxide loss in the first five months occurred at the same rate for the oak and Flextank vessels, showing the validity of Flextank's oxygen permeation physics and vessel designs.
There was no significant difference in wine colour density after 11 months, while the wine hue was higher in the Flextank vessels in comparison to the oak vessels. Levels of oak volatiles increased during the time course of the maturation study, irrespective of storage vessel type.
The concentrations of free dimethyl sulfide in the Flextank vessels were slightly, but not significantly, higher than in the oak vessels (8 to 10 microgram/litre compared to 6 microgram/litre). The measured concentrations of hydrogen sulfide were the same in all vessels and the levels of methanethiol were below detection._


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## ibglowin

It would be nice to see an unbiased study done by someone other than the manufacturer making the claim.


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## WellingtonToad

Do you really want to keep the "Angels Share"?
You need to think about this. I have a flex tank. I bought it based on the projected life. Barrels are expensive and difficult to clean. I still think a flex tank is the best option, but not because you keep the angels share.
As it happens I have a borrowed 220 litre barrel filled with water. (Made a lot of port and didn't need to use it again last year) It sat next to the flex tank all year and took about a gallon of water (with k-meta) top up per month.
This made me start thinking. The flex tank lost nothing.

The bung was firmly in place. The only way for the volume to change in the barrel was through the wood. If that is the case then surely molecular size is going to be significant. Of what is in the wine, the smallest molecules are CO2 and H2O.

To me, this means that the wooden barrel is actually increasing the concentration of the wine. Improving the flavour.

If you make kit wines this would be like reducing the amount of water you add.

If you use grapes, this is possibly the only way to remove water without affecting the flavour of the wine negatively. Certainly, the easiest.

I am happy with my flex tank, but there is a place for barrels. Just make your decisions for the right reasons.


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## GreginND

Of course concentration in a barrel is a factor to consider. It does affect the wine and is often desirable. 

I'm wondering how well flex tanks work for holding white wines vs steel for, say, 6 months or so? Is it people's experience that the oxygenation is good or detrimental?


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## grapeman

The flextanks have a heavier grade for whites with much less permeability.


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## altavino

In 2012 I did a side by side with my flex tank with staves in it and a one year old barrel and compared with a carbou of the same wine and aged them for a year.

Yes the free so2 levels dropped at more or less the same as the barrel . 

The micro ox effect of the flex tank is noticeable , the wine is smoother and tannins more integrated compared to the carboy.

Compared to the barrel the wine is a bit brighter and more fruit forward.
But in a nice way.
In a blind tasting 4 out of 9 preferred the flex tank . 

2 people couldn't tell the difference , me I preferred the barrel but was very impressed with the ft.

This was a Bordeaux blend . But if I was making zin ,Pinot or sirah , I'd probably flex tank it to keep the brighter fruit and light aromatics .


You don't always want any concentration effect , especially if you had any grape raisining / grape dehydration to start with , the preservation of the brighter fruit flavours and lack of concentration effect would be highly desirable in a crazy hot dry year.

For a white wine six months is good , if you need to go longer get the thicker tank. I like the flex tank for six months , it gives the wine a bit more mouthfeel and takes the acid edge off ( doesn't actualy reduce acid but reduces the nails on chalkboard brightness) Great for Chardonnay Viognier or high acid hybrids especially if combining with surlie (natural or biolees) . For Gewurtztraminer, Riesling or Pinot Gris , I'd stick with steel or the thicker tank.


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## Runningwolf

John, that was a great research project and very informative. Thanks!


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## altavino

I blended them together , the barrel, tank and carboy before bottling which worked out well.

I did bottle a case of each before blending to see how it develops individually as comparison to the main batch ( 45 cases)


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## geek

I am liking this even more....but it looks like the smallest vessel is 30 gallons.
I imagine someone needs to make about 32 gallons of wine and when all set and done after fermentation and racking end up with ~30 gallons to age and keep the container full.


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## sdelli

All the data you guys are showing has been provided by the FLEXTANK manufacturer! Of course it is written that way....... What else would they say!!!! The only data to consider was Altavino since his was un bios.... But still showed no great benefit over a barrel.


Sam


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## GreginND

sdelli said:


> All the data you guys are showing has been provided by the FLEXTANK manufacturer! Of course it is written that way....... What else would they say!!!! The only data to consider was Altavino since his was un bios.... But still showed no great benefit over a barrel.
> 
> 
> Sam



By benefit, you mean in the qualities of the wine? All things being the same and the wine turning out with the same quality, there are great benefits in terms of cost, cleaning and maintenance of flex tanks over barrels.


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## sdelli

GreginND said:


> By benefit, you mean in the qualities of the wine? All things being the same and the wine turning out with the same quality, there are great benefits in terms of cost, cleaning and maintenance of flex tanks over barrels.



Absolutely! My only concern is that there is any validity to their claim..... The only real data the end users have of this product is what was given to us from the manufacturer themselves! Breathable plastic is a hard pill to swallow. I would need to see some evaluation data from a third party before I could support their theory on this happening...... Not the CEO of the company making a statement on it! There are millions of diet pills on the market too..... None will help you loose weight for any period of time as promised!


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## altavino

You guys need to get out more .

Flex tanks have been independently tested in both the wine trade magazines . Wbm & w&v .

Most of the research came from early negative experience with oxidisation in plastic containers , changing the formulation and wall thickness allowed the dialling in of permeability rates upto and including exclusion. There is nothing complicated about it , basic polymer chemistry .

These have been used commercially for over 10 years and there use is becoming increasingly common, 1000 wineries in the USA alone according to w&v magazine . Commercial makers wouldn't risk hundreds of thousands of dollars if they didn't work.

If you don't believe oxygen can permeate plastic , take a finished carboy of wine , rack it into a plastic water jug like those used for office water coolers , fill it right up and put a solid bung in and seal it with wax .
Wait 6 months , then cry over your oxidized wine.


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## sdelli

altavino said:


> You guys need to get out more .
> 
> Flex tanks have been independently tested in both the wine trade magazines . Wbm & w&v .
> 
> Most of the research came from early negative experience with oxidisation in plastic containers , changing the formulation and wall thickness allowed the dialling in of permeability rates upto and including exclusion. There is nothing complicated about it , basic chemistry .
> 
> These have been used commercially for over 10 years and there use is becoming increasingly common, 1000 wineries in the USA alone according to w&v magazine . Commercial makers wouldn't risk hundreds of thousands of dollars if they didn't work.
> 
> If you don't believe oxygen can permeate plastic , take a finished carboy of wine , rack it into a plastic water jug like those used for office water coolers , fill it right up and put a solid bung in and seal it with wax .
> Wait 6 months , then cry over your oxidized wine.



I hear ya..... My comments were based on the information that his thread has brought forward. It is ALL based on the manufacturer information. I would be very interested in seeing more information on this type of storage from a different source if you have one! If it is indeed as good as you say and been around as long as you say..... The art of free competition in the great USA should have others as well..... And yes, a patent will not stop competition from creating a little different product of the same type if it has demand.


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## grapeman

Everyone needs to make their own decisions as to what to use based on their circumstances. Is this right for you, sdelli? That is your choice. Others need to make their own decisions. I have taken the liberty of finding another paper for you researching the permeability and wine qualities and it can be found here: http://www.moundtop.com/pdf/HDPE-oxygen-permeability-Flextank.pdf .


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## Runningwolf

Based off all the comments I have heard from winemakers who have them I would not hesitate to buy one. I also know numerous wineries that have bought them during start up. I also see altavino as a very trusted resource.


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## GreginND

sdelli said:


> Breathable plastic is a hard pill to swallow.



Decades of research and reams of data from polymer scientists on oxygen permeability of any kind of plastic you can imagine is in the scientific literature. 

I would say go to the library but you can start on google scholar:

http://scholar.google.com/scholar?q=HDPE+plastic+oxygen+permeability+studies&btnG=&hl=en&as_sdt=0%2C35&as_vis=1


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## altavino

The tall skinny nature of a flex tank makes for a good fermentation vessel for whites 
And for my Pinot noir I made a screen with a stainless frame that fits in the dexter top and do a submerged cap ferment .
This I blend with the wide fermenter Pinot before barreling


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## HillPeople

I have 30 gal. each of Amarone and Montepulciano going now in 30 gal FlexTanks.
We bought the floating skins for long term maturation. 
I'll let you all know early fall what I think of them, but I sure like them so far.
Using French barrel staves in each.


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## geek

It looks like you don't have them topped off ?


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## HillPeople

geek said:


> It looks like you don't have them topped off ?



They are still actively fermenting.
When that's done we'll rack, put in the skins and inert gas and seal them.


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## sdelli

grapeman said:


> Everyone needs to make their own decisions as to what to use based on their circumstances. Is this right for you, sdelli? That is your choice. Others need to make their own decisions. I have taken the liberty of finding another paper for you researching the permeability and wine qualities and it can be found here: http://www.moundtop.com/pdf/HDPE-oxygen-permeability-Flextank.pdf .



I am not trying to sway anybody decisions in any way at all.... I am just asking this thread to provide the more in depth resources they claim to have on this product. It would help me dramatically in making a decision in the future whether or not to move in this direction. Not just the one provided by the ceo himself. That is the great thing about the forum! It will help everyone collaborate a subject until the best answers have been uncovered.....


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## GreginND

sdelli said:


> I am not trying to sway anybody decisions in any way at all.... I am just asking this thread to provide the more in depth resources they claim to have on this product. It would help me dramatically in making a decision in the future whether or not to move in this direction. Not just the one provided by the ceo himself. That is the great thing about the forum! It will help everyone collaborate a subject until the best answers have been uncovered.....



Well, that's fine. And I think getting personal experience on the use of flextanks from other winemakers is great. But it seems that you discount the science of oxygen permeability without doing the research expecting all of us to convince you. And you are immediately skeptical and reject studies that have been presented because some are done by the company selling the tanks presumably without actually reading the details of the experiments and determining if their methods are valid.

I guess I would suggest that you do a bit of the literature searching yourself and if you question the results, tell us why you doubt the data. Do you think they are fabricated? Do their results conflict with published studies on permeability of HDPE in the literature? Of course independent confirmation of the studies would be ideal. But I would also say that ordinary claims require ordinary evidence and extraordinary claims require extraordinary evidence. The studies done by Flextank and their partners are what one would expect based on the properties of HDPE, so I don't see anything extraordinary about their claims.

All that being said, I would caution anyone from making conclusions solely based on organoleptic qualities of the wine in flex tanks. Tastes are often subjective. Hard data (measurements of SO2 levels, measurement of O2 levels) are more convincing.


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## geek

HillPeople said:


> They are still actively fermenting.
> When that's done we'll rack, put in the skins and inert gas and seal them.



what exactly is floating skins? Are you referring to grape skins pack?
So you plan on putting them after fermentation?

Thanks for the clarification.

.


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## ibglowin

LOL, no………..


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## geek

uh? New one for me, kind of like a balloon uh?


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## altavino

The floating skins give a variable capacity ability they sit on the surface of the wine reducing headspace issues , saturating the headspace with an inert gas gives further protection .

I put the skin on after I've racked the wine off the gross lees and into the tank , innoculate mlb and conduct mlf with the skin in place .

That said , it's still preferred and much lower risk to use the tanks completely full and you really have to watch your so2 levels. 

I've got the dexter tanks , hill peoples are the ECO tanks , different lid but cheaper priced than the dexter , both are good . I wanted the bigger opening .

Flex tanks are also great because they are easy to clean , don't plug up like the pores of a barrel and don't dent like a stainless vc tank . I've backed into them with a forklift without issue . Tough gear.

Are they perfect? No . But neither are barrels or vc stainless tanks . 
They offer some advantages and are litre for litre , cheaper .
But if you only make a couple carboys worth a year stick with those.

One thing I like is the flexibility , once you buy a barrel you have to keep it full until you scrap it. A flex tank can sit empty one season to the next without issue .
I've got enough barrel capacity to make 1.5 tonnes of grapes into wine . This year I also made some white wine and a winery gave me a great deal on 800 lbs of California grapes that I'd like to use as blender with our local stuff .
Having the two flex tanks means I could go big this year but since I only make white every 2 or 3 years and I'm not making as much red next year those flex tanks can sit idle .
They are also good blending tanks and fermenters , something barrels are not. 

Pros and cons . But a great economical tool for the larger scale amateur . 
And I'll be long retired from winemaking by the time they wear out.


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## Runningwolf

I wish you guys would quit talking about these. It's just a good think I can't buy them local "hopefully they won't be at the Winemakers Magazine convention either). I would really seriously think about buying one. Currently I am using SS beer kegs (15g) that can be picked up for $30 if you hit the right salesperson at the local beer dist. Perfect for wine? Yes! But it does not have the extra bells and whistles you can get with a Flex Tank.


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## altavino

http://morewinemaking.com/category/speidel-plastic-tanks-1.html

Seidel tanks are good for smaller volumes but have a similar o2 permeability as the HD ft, I have one 60l 
They chew through so2 a faster than a carboy but fine for 8-12 month storage .

They are small too


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## semenn

Interesting topic. It's not clear why everyone suddenly decided that a plastic tank should work just like an oak barrel? In my understanding, these are two complementary technological units. I'll tell you my experience.
*I make and use a tank made of polypropylene in winemaking. My tanks have a conical bottom for easy removal from the sediment and a floating cover with a pneumatic seal chamber, which allows the use of a smaller volume without the risk of oxidation. These tanks I use in the initial stage of winemaking. The main advantage is the use during fermentation and maturation, as well as the possibility of easy removal from the sediment and cleaning from the fallen stone. I use a polypropylene tank from autumn to early spring, after which I pour the wine into glass bottles or into an oak barrel for further maturation.


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## ibglowin

This is a really old thread you have replied to. I actually have 2 of the 15G Flextanks now. They do allow micro-oxidation at about the same rate as a barrel of the equivalent size. They provide everything except for concentration through evaporation (Angels Share) Nice thing about these is that unlike a barrel you can use them one year and then rinse them out and store them for however long it is until you need them again. 

Try that with a barrel.


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## semenn

In addition to micro-oxidation, the oak barrel adds tannins to the wine. These are slightly different processes. The more urgent purpose of the plastic container is to work at the initial stage. The aging process is best left to the oak barrel and the glass bottle.


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## ibglowin

Tannins can be added from a bottle or from oak adjuncts. I own 4 barrels myself but I find the Flextank to fill an important need in my winery.



semenn said:


> In addition to micro-oxidation, the oak barrel adds tannins to the wine. These are slightly different processes. The more urgent purpose of the plastic container is to work at the initial stage. The aging process is best left to the oak barrel and the glass bottle.


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## semenn

In my understanding, a flex (plastic) tank does not replace a barrel, but is an essential equipment in the initial stage of winemaking.


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## ibglowin

You might need to rethink things then.



semenn said:


> In my understanding, a flex (plastic) tank does not replace a barrel, but is an essential equipment in the initial stage of winemaking.


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## semenn

Most likely, I do not see the proper benefit from having the processes of an oak barrel transported to an artificial environment. But everything can change with time. So I'm talking about my opinion on the use of plastic tanks at the moment.


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## ibglowin

Yes! Good way to phrase this exchange I would say.



semenn said:


> So I'm talking about my opinion on the use of plastic tanks at the moment.


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## sdelli

We can compare the process of micro oxidation from flex tanks to barrels. But that is only part of the equation. I do not believe you can achieve in today's technology the duplication of a good oak barrel with cubes or sticks..... I use both all the time.... They are different.


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