andy stone wrote:
> What roughly would be the minimum weight ratio of sugar to orange peel, when
> making marmalade; which would be enough sugar to preserve it sufficiently.
> Thanks.
>

I've used Seville oranges to make marmalade, but I didn't like it
because it was too bitter (I know it's supposed to be bitter.) The best
luck I've had is with tangerines:

Bob's Tangerine Marmalade

2 pounds tangerines (I used "Honey" variety)
2 largish lemons
6 cups water
8 cups granulated sugar
1/2 cup bottled lemon juice

Scrub tangerines and lemons to remove any wax or pesticide residues.
Simmer whole tangerines and lemons in 6 cups of water, covered, for a
couple of hours, then let them cool enough to handle. Cut the cooked
fruit in half and scoop out the pulp and put it back in the cooking
water. Set the tangerine peels aside for later. Discard the lemon
peels or save for another purpose. Simmer the pulp and seeds for about
a half an hour, mashing occasionally with a potato smasher. Strain the
juice out of the pulp with a jelly bag or big square of muslin cloth,
squeezing it as dry as possible. Slice the cooked tangerine peel into
slivers and added to the strained juice in a large shallow stock pot.

Bring pulp, juice, and peels to a boil, add sugar all at once, and cook,
stirring until the sugar is dissolved. Taste, and adjust tartness with
up to 1/2 cup bottled lemon juice ("Honey" tangerines are not very sour
at all.) Cook until 222 degrees on a candy thermometer, let cool to
about 200 degrees, and ladle into half-pint jars. Adjust caps and
process in boiling water bath for 10 minutes. Makes about 8 half-pints,
with a little left over.

Notes: All the peel floated to the top of the jars during processing,
so I shook them and turned them upside down after they went "ping".
Blue ribbon winner, Olmsted County Fair, 2004

--
Best regards,
Bob