Choosing a filter grade or porosity to start your filtration, and then picking the subsequent step-down grades can be challenging.

One way to approach which grade to choose is by taking meticulous notes for every filtration to improve your gut feel and anecdotal experience of filtration. From this experience, you might be drawn to certain grades. For example a K700 micron to a K200 to an EK. Another popular step-down
is a K800 to a K250 to a KS50. Or if you choose to have more than three passes a K900 to a K300 to a K100 and then the EK is also a well-known path. You want to avoid skipping more than three grades per pass. For example, going from a K900 to a K200 or a K700 to a K100 is too big of a jump and your throughput on the tighter grade will be less than optimal.

Using your trusted sequence over and over might not be the right fit for every product or even the same product over different vintages or batches.


  • A good pre-clarification program that is not limited to multiple rackings, using a smart fining program (which doesn’t have to change your product, only clarify it) or just plain old time and gravity, can all help to minimize passes through filter media.
  • The more scientific approach in choosing porosity is to measure the turbidity of the product to get an idea what the percentage of suspended solids are, and then use the guide below to choose the proper grade. Starting too tight may strip your product of color, mouthfeel, and flavor. In addition, throughput would be less than stellar. Starting too coarse could result in very little change in turbidity and wasteful passes in filtration when fewer could’ve gotten the job done.
  • Although turbidity is a good indicator of clarity, it doesn’t provide much information about the types of colloids you are dealing with. It is also not the silver bullet to guaranteeing that you will plug the filter grade you chose.
  • Colloids make up most of the things we love like color, flavor, mouthfeel, and weight. But, there are also specific colloids like beta-glucans that are produced by Botrytis that can wreak havoc on even the coarsest filter media. They require a quality beta-glucanase enzyme, such as Lallzyme MMX, to keep them from ruining your bottling day (it’s important to note that the contact time for this specific problem colloid with the Lallzyme MMX is 6 weeks). Another colloid that can be quite detrimental to filter media is pectin. A good pectinase early in the production process, and/or after fermentation can improve throughput dramatically. Just using a pectinase before or during fermentation isn’t always enough since pectins come out of solution in the presence of alcohol and at low temperatures. Good filterability enzymes to have in your toolbox are Scottzyme KS and Scottzyme KS Plus.
  • Turbidity analysis can be measured at a lab or with your own nephelometer, which is available in handheld and bigger benchtop models.

To ensure a trouble-free bottling day, view our Bottling Day Checklist for comprehensive instructions on proper pre-filtration and timing for bottling.

Please contact Scott Laboratories for assistance with choosing the right fining agent or enzyme for your product. We strongly recommend bench trials and taking notes for every filtration.

Note: Some producers, like breweries, who just want a bit of a polish and don’t plan to go through a sterile filtration by means of an absolute cartridge filter, do a single pass through a medium grade porosity before going to their final packaging. Usually, these producers have an effective fining program in place so that they are able to filter less, and at the same time, have minimal stripping of color, flavor, and mouthfeel. The other bonus is that they will have an increased consistency in clarity over the course of the filtration.

GradeTurbidityScottSeitzParticle Holding SizeBiology
Coarse<100 NTUSE 9.0K9009 - 20 μmYeast
Coarse<80 NTUSF 8.0K8008 – 18 μmYeast
Medium<60 NTUSG 7.0K7006 - 15 μmYeast
Medium12 - 35 NTU SM 3.0K3004 - 9 μmYeast
Medium10 - 20 NTUSR 2.5K250 or ZD25 3 - 8 μmYeast
Fine1 - 10 NTUSX 2.0K2002 - 6 μmYeast
Fine1 - 2 NTUSY 1.0K100 or ZD10 1.2 - 3.5 μmYeast
Fine1 - 1.5 NTUST 0.8KS80 or ZD80 0.7 - 1.5 μmYeast
Sterilizing 1 NTUST 0.5KS500.5 – 0.8 μmYeast
Sterilizing <1 NTUST 0.45EK or ZDEK0.4 - 0.6 μmYeast
Sterilizing<1 absolute ScottCartMembracart0.45 μmYeast/Bacteria 

Please Note: This chart is a guide only. Wine chemistry can affect filtration despite turbidity results. Colloids and other charged species will not contribute to turbidity but can block filters.