I make my own vanilla extract all the time. Based on my experience, I can say without a doubt that 1 bean per 8 oz will surely make a very anemic extract. I use a whole lot more beans than that.
Here in the USA- as per the FDA's specs for commercial 'pure vanilla extract'- the ratio between beans to alcohol is 13.35 ounces in weight of beans to 1 gallon of alcohol (for single-fold extract). Whittled down, that means .8 oz (23g rounded up) in weight of vanilla beans to every 8 oz. (227g) alcohol..... for single fold.
To make double-fold, I would need 1.6 oz (45g) beans in weight per every 8 oz (227g) alcohol.
To make triple-fold, I would need 2.4 oz (68g) beans in weight per every 8 oz (227g) alcohol.
The above ratios are as per the FDA regs (whittled down to a more manageable size)....... but I go one better. These are the ratios I prefer to use:
: 1 oz. (28g) weight of beans per every 8 oz (227g) alcohol.
- 2 oz (57g rounded up) weight beans to every 8 oz (227g) alcohol
- 3 oz (85g) weight beans per every 8 oz (227g) vodka.
For what it's worth, I mostly make double fold, and it's awesome.
I use grade B Madagascar beans, which are plenty good enough for the task (you definitely don't need the more expensive grades for extract, by any means), and I use cheapie 80-proof vodka, which gives my extract a 40% alcohol content....only 5% more alcohol than the FDA regs if one were going to sell the extract commercially.
After weighing my beans I split them down the middle with a knife to open them up and expose the seeds, then I toss them all in an appropriately-sized canning jar for the job, and pour in the appropriate amount of vodka in weight over them. Then I tightly cover the jar, give it a good shake, and set it in a dark cupboard to steep (giving the jar a shake whenever I think of it).
As far as length of steeping time goes, longer is always better (just like with soap). I usually let mine steep 3 months before using. You can use it earlier than that, but I would wait at least
1 month at the earliest before using.
Here's a pic of my extract (double-fold):