What I'm trying to find out is how much MORE toner is used on a
photocopy that is totally black than on an average photocopy of
printed text.  (The point is I want to find out how wasteful chunks of
black on photocopies are).

Hi drpulp --

The search term you needed to know to find your answer was "coverage."

Coverage refers to the percentage of a page's surface that would be
covered if you squashed every bit of its ink into one place.

==============
STANDARDS
==============

When we talk about text coverage, we're talking about standard 10
point text with 3/4 inch side margins and 1 inch top and bottom
margins.

Typically, if you squeeze together all the black in a regular black
and white copy of a double-spaced business letter, its coverage will
be 5- 6 percent. The industry standard (used for predicting and
comparing toner usage) is 5%.

Another International Standard that is used to compare toner coverage
is the "Dr. Grauert Letter (ISO 10561). This is a German business
which has a coverage of about 3.2 % :

DR. GRAUERT LETTER
http://www.heise.de/ct/ftp/02/10/200/Org_Faelsch.jpg


==========
VARIABLES 
==========

SPACING – if you use single spacing you double your coverage, and
hence, the amount of toner used.

EMAIL – tends to use more toner because of long paragraphs, bold text,
single spacing, headers and ruling lines. Coverage may be as high as 9
or 10 percent.

WEB CONTENT: could require upward of 30 percent page due to small
crowded text and graphics.

COLORED PAPER FOR ORIGINALS – This gives you a cloudy copy and uses up
toner at a higher rate.


=============
RESOURCES
=============

These sources discuss both copiers and printers. Realize that as long
as you are still talking black toner on white background, the coverage
percentage is the same.


BUYER ZONE – COPIERS - So what's coverage?  [scroll down for that
section]
http://www.buyerzone.com/office_equipment/copiers-color/buyers_guide5.html

-------------------

" …The page count rating by the manufacturer of your toner cartridge
is rated at 5% page coverage. This means optimized print density,
double spaced text only, and letter sized paper. If you single space
your text, you double the page coverage and cut your rating in half.
Using graphics uses tremendous amounts of toner, and you may get as
little as 1/4 of the actual rating if you print pictures and lots of
bold print. On copiers, if you are copying from a colored paper, and
the color from the paper creates a hazy background on your copy, that
haze is toner being used and will minimize your page count."

HOW TO GET THE MOST FROM YOUR COPIER AND LASER PRINTER
http://www.inetsupermall.com/inkjets/laser.htm

---------------------

" one of the most common print jobs is email, and some emails may
require toner coverage as high as 9 or 10 percent. Similarly, printing
news articles from common Web sites could require upward of 30 percent
page coverage…."

LASER BUYERS BEWARE
http://www.okidata.com/mkt/html/nf/ARSReport.html

--------------------------

So, that should give you a good indication of how a typical text copy
compares in toner usage with a 100% black page.

If anything I've said isn't clear, please feel free to ask for
clarification using your CLARIFY QUESTION button.

Thanks for your question!

-K~

search terms using GOOGLE:

percent toner coverage page
"Dr. Grauert Letter" coverage

Search terms in GOOGLE IMAGES
"Dr. Grauert"

I was shocked at how fast my researcher answered.  The language he/she
used in the repsonse was clear and conversational.  Great job.  I will
use the service again.