Oak barriques soften wine by diffusing 20 to 30 mg. (15 to 23 ml.) of air-oxygen per liter of wine per year (mg/l/yr) through their micro-porous staves. This natural osmotic permeation is driven by the higher partial pressure of oxygen outside (0.2 atm) to inside the barrel (~zero), as wine "consumes" all the available oxygen that diffuses in. Permeation provides MOST of the oxygen entry into a barrel. Repeated topping only adds about 5 mg/l/yr and splashing/racking about 4 mg/liter each time.

Successful wine maturation requires an "oxygen rationed" environment, rather than "all at once" oxygen exposure, which instead catalyzes acetaldehyde formation and causes aerobic bacterial spoilage i.e. by Acetobacter, always present in small populations in wine (unless sterile filtered). Smaller barrels allow oxygen to diffuse in at a faster rate per liter of wine in them than larger barrels, due to their higher surface area to contained volume. Metal tanks allow no permeation, instead requiring micro-oxygenation.

The typical wall thickness of the special C-P polyethylene used in these vessels, 0.16", diffuses oxygen from the air at about the same rate as a typical new oak with 3/4" thick staves (see below). However it is a one way effect. The C-P material does not allow evaporative loss of wine components so these vessels DO NOT NEED TOPPING.

In addition to needing no topping, Flextank maturation vessels PREVENT flavor and aroma molecules from leaving the wine. These most delicate of wine components (i.e. the fruity ethyl esters and aroma compounds) are largely lost to the atmosphere when wine is matured in oak barrels. The quite heady "wine/wood" aroma in typical cellars signals that loss of wine aromatics, which leave the wine continuously.

There is no aroma associated with use of Flextank maturation vessels, thus users over multiple vintages report SUPERIOR matured wine quality over top quality French barrels and many have the prizes & trophies to prove it!.

These vessels pay for themselves very quickly:-

• no "aging out", indefinite usable lifetime
• much higher cellar storage density
• no loss of valuable wine volume by evaporation
• almost complete elimination of barrel room labor
• greatly reduced cost of wood (less than 8 cents per liter compared with more than $1 per liter for wood in the form of barrels)
• much more consistent performance, vessel to vessel, year by year

Given that wine quality is being proven over time to be SUPERIOR to the same wine matured in barrels, your purchase decision is self-evident!

Vessel Specifications and Prices (add GST)

The HDPE polymer microstructure (see below) consists of long-chain, wax-like hydrocarbon molecules in a semi-aligned relationship with each other. The long molecules have only enough interstitial space to allow "small" gas molecules to permeate through. The 300 gallon and 600 gallon C-P vessels are deliberately elongated in their geometry to have enough surface area per gallon stored, to "mimic" the average age 2 to 3 seasons-old barrels in most cellars.

Free surfaces in barrels or tanks allow air-oxygen to dissolve in wine at rates thousands of times greater than the rate it diffuses through solids. Even with CO2 in the head-space, there is usually still enough oxygen present, (CO2 dilutes air rather then displacing it), to cause aldehydic wine near the surface and to enable aerobic organisms to multiply on the surface, causing scum.

Flextank maturation vessels are therefore supplied with a floating disk-shaped flexible insert ("Skin") which is lowered into the wine after the vessel is filled into the top chamber. This blocks almost all of the free surface, suppressing scum and bacteria.

For safe use part-filled, a full body sized "Variable-Capacity Skin" will sufficiently reduce the exposed wine surface for the bulk of the wine to protect itself (with free SO2 in the wine). Most users flush the head space with CO2 when using V-C Skins. Flextank V-C Skins have been in use for 4 vintages and have proven to be highly effective.

NOTE: In maturation vessels of 1,000 l. or smaller, operating part filled with a V-C "Skin" installed will require more frequent SO2 adjustment than with either full barrels or full maturation vessels. SO2 consumption typically about doubles in that situation.

600 gallon maturation "Cells" are FAR more compact to use than barrels. The image below is a same-scale comparison of the space required for 8 x 60 gallon barrels in a "legal" 4-high stack, compared to 1 x 600 gallon Cell which holds 25% MORE wine, i.e. the equivalent of a 5-high barrel stack. The right hand image shows filled Cells saving space in a barrel store.

These narrow 600 gal. Cells can be stacked together sidewise like books in a bookshelf, optionally locked to each other. They can also be stacked two-high vertically.

300 gallon "Rockets" can be set up in pairs, optionally on pallets, with aisles between for wheeled stock picker access (see Tank Accessories page).

Replacing barrels with Flextank cells can potentially increase the storage capacity of a high-headroom barrel hall by more than a factor of five.

The gross lees level in these vessels is clearly visible, as is the fill level, making racking a simple task. A racking plate can be used on the end of a pre-measured length of hose, or the Flextank submersible racking pump can be simply lowered into the vessel, pre-set for height off the floor.

Flextank's special HDPE material is very easy to clean, tartar doesn't stick and the material doesn't stain. There is no porosity or "grain" to clog. These vessels retain their gas permeability indefinitely. The material is also sterilizable with boiling water or steam and/or sterilizing chemicals, allowing persistent bacterial or yeast infections such as brettanomyces to be removed completely for safe re-use.

Substantial water savings are normal. Unlike oak barrels, these vessels do not require "wetting out". They clean out quickly and easily with a few liters of mild caustic as a rinse to decolorize them and a brief fresh water spray to flush solids out.

Unlike oak barrels, C-P vessels DO NOT require SO2 treatment when stored empty for long periods. They also DO NOT allow any internal liquid to pass through to the surface and evaporate away, so they do not require topping.

Manufacturing commenced in August 2006 in Chowchilla, California, located close to the major wine producing regions. However Flextank's chosen contract molder has 4 plants around the country and from time to time, molds will be moved to these other locations to build up stock.