[Community_garden] coffee grounds are NOT highly acidic

[yarrow at sfo.com]

  How curious that the tested pH of coffee grounds was so different 
from the east-coast lab. Maybe east-coasters drink their coffee much 
weaker, so more acid remains in the grounds?

Sunset magazine had Starbucks coffee grounds tested at Soil and Plant 
Laboratory Inc., Bellevue, WA, and the pH was 6.2. 
http://www.sunset.com/sunset/garden/edible/article/0,20633,1208232,00.html


Ray Schutte wrote,
>....Starbucks commissioned a study in 1995
>to better understand the make up of the
>organic matter we call coffee grounds. The
>following is the result of the analysis
>performed by the University of Washington,
>College of Forest Resources:
>....Most of the acidity in coffee is removed
>during the brewing process. Used grounds
>have an average pH of 6.9.

Mike McGrath wrote:
Wood's End Lab has confirmed that coffee grounds are VERY acidic;
[They came out at 5.1, a perfect low-end pH for plants like 
blueberries that thrive in very acidic soil. "But that's the most 
gentle result we've ever found," Will quickly added, explaining that 
the other 31 samples of raw coffee grounds they've tested over the 
years all had a pH below 5,]

I wrote, quoting
>>  http://faq.gardenweb.com/faq/lists/soil/2002015354019975.html
>>  The measured pH of used coffee grounds was 6.9, with a significant
>>  amount of buffer capacity - adding the coffee to either acidic or
>>  basic solutions drove both towards neutral pH....."