First, make sure that the portion left over, i.e. the portion you are not bottling now and will be adding more oak to, will be stored in a completely full (or “topped up”) container. This is critical to protect wine, especially white wines, from the ravages of oxygen and aerophilic spoilage organisms. Now, on to how much more oak you should add and how much time it will take to notice the effects. You can always add more oak but you cannot remove it. For that reason, start with one pack, waiting two weeks and stirring and then tasting for oak flavor and aroma development. If you sense that this one pack is moving you in a positive direction, don’t add the second one quite yet.
I don’t know how many grams of oak chips are included in each “pack” you refer to, so it’s hard for me to give exact recommendations, so here are some general guidelines. In Chardonnays that are approaching bottle readiness, I find a 2 g/L oak chip addition will give a satisfying hit of oak without being too heavy, in about 6–8 weeks’ time. When using any non-barrel method of introducing oak into wine at any stage, remember these guidelines:
• The closer a wine is to being bottle-ready, the more an oak addition will have an impact on the wine. Be conservative when adding oak in the later stages of a wine’s life pre-bottle.
• The earlier in a wine’s lifetime you add the oak, the better-integrated it will be. This also allows you to add small amounts little by little, therefore avoiding over-oaking the finished wine.
• The smaller the oak particle, the faster the extraction time. Powders have an almost instantaneous effect. Big tank staves can take months to fully extract. Though a small particle may seem like the best option, I often find the best wine quality results in aroma and flavor come from using larger particles, like “segments” that are about two inches square, or even larger pieces sometimes packaged in oak “fans,” or small staves about 18 inches long, ¼ inch thick and 2 inches wide which are attached together at one end with a ring. A great all-around product for home winemakers (because they fit into a carboy neck or barrel bung hole) are the small cubes or “beans” about 1⁄2 to 3⁄4 inch on all sides. They give some of the nice “bigger particle” oak flavor while being easy to handle in the cellar.
• The higher the alcohol, the faster the extraction time. Ethanol is a far more powerful solvent of oak than water. Be cognizant that a Chardonnay of 15% alcohol may need about a quarter less oak extraction time than a low-alcohol white wine at 11%.
• Stir and taste periodically to monitor progress. You need to make sure that you stir up your container (minimizing oxygen contact) and taste regularly to get an idea what the oak is doing to your wine. Be sure you just don’t thief out a sample at the top of your carboy where the oak might be floating or you’ll get a false sense of a higher oak concentration. Judge how often you taste based on your oak extraction timeline. If you have added oak to a newly-fermented wine and have planned on aging it for many months, tasting monthly should be fine. If, like you, you’re doing a pre-bottling oak adjustment and especially if you have added an aggressive amount of oak, taste every five to ten days to make sure you are not over-oaking.
• Do bench trials. Sometimes toast levels will surprise you and you’ll find a high toast product actually is the perfect thing for your Chardonnay. You may love American oak on your Zinfandel but hate it on your Viognier, or vice versa. For oak trials, I use 375 mL sample bottles and try to weigh out 2, 4 and 6 g/L amounts of my oak product and add to the wine, letting it sit for a week. Though these are higher doses than you will probably put in your finished wine, with a week’s contact time it will allow you to see in which direction that oak product is taking your wine.