Re: minimum interword spacing for a whole document?

[Jeff Kingston]

The normal interword spacing is the width of a space character
in the font.  One option would be to increase the width of a
space in the font metric file for your body text font.  Another
would be to hack source file z14.c by changing the line

    #define     SQRT_TIGHT_BAD      128

to, say,

    #define     SQRT_TIGHT_BAD      256

to increase the penalty for tight lines.  Ignore the
"#define TIGHT_BAD" line, TIGHT_BAD is no longer used.
In z14.c there is also

    #define MAX_SHRINK  4

which is saying that Lout is willing to reduce the width of a space
to a minimum of 1 - 1/4 of its usual value (although this will of
course attract a large penalty).  You could increase this to 5 or 6
and see what happens.  It's all a balancing act, however, so other
things might come out looking worse.  Your publisher might start
complaining about excessive hyphenation or loose lines.  You have to
fiddle around, which is what I did when setting these numbers long ago.

Jeff

ps I hope your publisher is proof-reading hard copy.  Inter-word
spaces that look too small on screen often look OK on paper,
owing to the tendency of screen previewers to move the positions
of characters to the nearest whole pixel offset.