[ynotbrusum]

I have a Flanders Red that lacks enough sour.  I know I can brew another and blend (which I will be doing), but for a portion of it, I am considering adding some lactic acid at bottling in a couple months to get some additional sour to it.  I am thinking of using an eye dropper in a small glass sample and extrapolating from there.  Does anyone have experience with this?  Does it help or should I just wait and only blend instead?

[kramerog]

You may get more sour in a few months.  Anyway, an eyedropper in a glass should work.  You'll need to figure out how many drops are in a ml.  Next figure out if what 1 drop/glass is equivalent scaled up to the amount of beer you want to sour.  If it works out to be a reasonable increment of lactic acid (5-10 ml would be great) then proceed with your experiment.  If it turns out to be unreasonable (let's say 100 ml) then use a bigger glass. 

[ynotbrusum]

The Flanders is coming up on 11 moths, so I think it was short on Lacto (I used a friend's slurry)... I have heard that is a risk on a repitch of Roselaere... Thanks for the input!

[reverseapachemaster]

How old is it? My first thought is that it just may not be old enough that the pedio hasn't had a chance to finish souring the beer and/or the beer hasn't been dried out enough by pedio and brett to make the sourness stand out.

Lactic acid certainly will add more sourness to the beer but I would be cautious about adding too much. Keep in mind that you are just adding acidity with no other flavor components than the acidity itself so not only will you change the ph but you'll also change the flavor. I would add it directly to the beer ahead of packaging and add a small amount, let it dissolve for a few hours and then taste check and test the ph.

[kylekohlmorgen]

+1

As brett continues to work, the finish will dry out, and the acidity will shine through. Allowing the beer to dry out will also make carbonation levels more predictable over time.

This is my opinion because I like my Flanders ales on the dry side. If you prefer a bit more mouthfeel (Petrus Oud Bruin instead of La Folie, for example), you might adjust the acidity levels, prime and bottle with fresh yeast to carbonate, and store cold after carbonation is complete. Some (most?) classic Flemish examples are filtered/pasteurized, so it depends on your goal for the finished beer.

If you're going for a BJCP competition winner, you'll have to ask a proper judge. I know my version (very Gueuze-like in its carbonation, dryness, and acidity) was a perennial loser in the category. 
 

How old is it? My first thought is that it just may not be old enough that the pedio hasn't had a chance to finish souring the beer and/or the beer hasn't been dried out enough by pedio and brett to make the sourness stand out.