Ask Wine Wizard

How is Fume Blanc made? I would like to make some at home!


Mike Johnston — Watsonville, California asks,

I have a 2003 Chardonnay aging in my garage. I have about 65 gallons, which I initially fermented at about 40 degrees F (4 degrees C) for four months and then moved to oak. The wine fermented slowly and is now at 1% residual sugar and has completed malolactic fermentation. It is a very fruity, semi-sweet wine that is no longer fermenting. Rather than attempting to restart fermentation, I am inclined to bottle it as is. I don’t want to mess it up trying to get rid of the residual sugar. I have just purchased a filter system. The finest filter pads that it has are 0.5 micron nominal. I understand this to mean that it will stop half of the 0.5 micron particles. Is this fine enough for sterile filtration so that I can bottle this wine without worry of fermentation starting in the bottle? And do you think I should even put my wine through a sterile filtration?

Wine Wizard replies: The short answer to your question is: 0.45 micron nominal filter pads are the industry standard for “sterile” filtration. These pads prevent all yeast and bacteria from getting through. So, if you want to be as certain as possible, it’s best to filter with a 0.45 micron nominal pad. This will ensure that you take out the maximum amount of unwanted material. The 0.5 micron filter sheet is a little bit “looser” than the 0.45 micron sheet and would most likely allow some microbes to pass through. If I was a winery with 50,000 gallons of 1% RS (residual sugar) Chardonnay that I wanted to bottle and put into the market, I would certainly make sure to final-filter with the tightest pads possible. Ruining thousands of customers’ opinions about your products due to one little yeast cell is a scary prospect. However, as you might imagine, I’ve got a longer answer for you and you can choose what option best suits you. You’re a home winemaker with only 65 gallons of the 1% RS Chardonnay, not 50,000