How to Choose a Bladder Press

Last Updated: 6/2021

Applies to: This guide is for wineries evaluating bladder presses. It includes general considerations and details on the Willmes presses represented by Scott Laboratories.


Choosing a press is one of the most important decisions a winemaker can make. The average press will last over 20+ years with proper maintenance and service. It is important to select a press with current technology, ease of use, easy to clean and easy to maintain, and provides high quality juice, helping to ensure high quality wine.

How will you fill your press?

Wilmes presses can be filled two different ways: they can be axially fed in which juice and grapes are pumped directly into the press cavity. This works well for machine harvested fruit. Alternatively, they can be fed through the press doors, which is common for whole-cluster pressing.

What capacity will you need?

If you are interested in machine-harvested and axially fed operations, sizing your press can depend on the following:

  • What size is your typical press load of machine harvested fruit?
  • How many tons are in your larger/largest lot?
  • How many press loads are you running per day?

If you plan on pressing whole clusters and prefer your press to be filled via doors:

  • What is the typical lot size for whole cluster fruit?
  • What is the largest lot size of whole cluster fruit? Are lots kept separate or are they blended?
  • The number of press loads per day depends on number of lots and lot sizes.

Willmes and Scott Labs

Since their founding over 100 years ago, Willmes has focused exclusively on wine presses. They have developed most of the new technology that is currently available in the market today. Scott Laboratories and Willmes have been in collaboration for over 40 years in the North American market with over 500 presses installed.

The Willmes Sigma presses with Flexidrain technology have been used in the wine industry for almost 15 years. Willmes is the only major press company to focus exclusively on wine presses – making them the industry’s leading specialists in pressing technology. Scott Labs offers two Willmes presses, the Willmes Sigma and the Willmes Merlin:

Willmes Sigma

The Sigma sizes range from 300-3400 Liters and comes fully automated. All press cycles are controlled via the intuitively designed touch screen with full color details of each press operation.

Willmes Sigma represents the next generation of pressing technology for wineries who are looking for:

  • Simple controls
  • Easy operation
  • Cleaning program that eliminates the need to enter the press itself
  • Ability to change parameters during operation
  • Completely automated programming
Special features included with the Sigma press:The Sigma has a patented double membrane system. Advantages:Additional optional features are also available, including:

Pomace evacuation bars

Control device for emergency bypass

Juice pump control

Cleaning program (CIP)

Rocking program

Universal connection to juice tray

Touch screen control panel

Shorter pressing times

Increased filling capacity

Up to 70% decrease in fine lees

Decrease in harsh phenolics

Increased yields with lower membrane pressure

Door ventilation valve

Tandem controlled second door

Independent controlled second door

Axial filling valve

Leg extensions

Juice outlet at drive end

Sigma Fill/Drain Position

The filling position on the Sigma Press is also the draining position. Relaxation of the membranes after pressing allows the pomace to gently crumble under its own weight prior to rotating. Fewer rotations are required which equates to lower solids and reduced skin phenolics. Juice travels half the distance of a conventional press due to the flexidrains. Up to 95% yield can be achieved at less than 0.8 bar. A typical Sigma customer reports full yields at less than 1.3 bar.

Sigma Double Membrane

The double membrane feature of the sigma press allows it to use 50% less air pressure to achieve 35% shorter pressing times and 10% higher yields.

TOP LEFT: see filling position of Sigma press, allows fruit to crush under its own weight and drain while the press is filled.

TOP RIGHT: See the pressing action of the double membranes.

BOTTOM RIGHT: Alternative rendering of double membrane pressing action.


The Willmes Merlin press is known for extremely low maintenance costs and designed for the smaller premium winery market. Press sizes range from 1200 liters up to 5000 liters. The Merlin uses a unique membrane which minimizes pressure, reduced amounts of lees, shorter pressing times and up to 25% additional filling capacity. Features include:

  • Juice pump control
  • Control device for emergency bypass
  • Rocking program
  • Universal connection to juice tray
  • Touch screen control panel

The Merlin press operations are fully automatic. The press doors are manually removed to allow easy filling of the entire drum. All press cycles are controlled via the intuitively designed touch screen with full color details of each press operation.

The following options are available:

  • Control console with 5 meters of cable
  • Control console with swivel arm
  • Juice trough on wheels
  • Axial filling valve
  • Leg extensions
  • Hoppers and catwalks

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