In Iowa, wild black raspberries (not the same thing as black berries) are quite abundant. You can even pick them for free along side hiking trails. I figure that with such an abundant supply, there is no excuse for me not to include raspberries in my canning.
Since strawberries and black raspberries are the most plentiful berries at my house, I decided some time ago that I wanted a jam recipe that used both of these. At that time, I didn't find a recipe I liked so I halved the ingredients in a recipe for strawberry jam and also halved ingredients for a recipe for black raspberry jam, and then combined them. This initially created a recipe that called for 3 cups crushed strawberries, and 2 cups crushed black raspberries.
I have since decided that it doesn't really matter what ratio I use. As long as I have a total of 5 cups crushed berries, the jam sets ok. Therefore, I am choosing not to specify the quantity of each berry in today's recipe.
I believe that the recipe would probably turn out equally well with red raspberries.
Strawberry and Black Raspberry Jam (Yields about 8 half-pint jars)
Enough strawberries, and black raspberries to make a total of 5 cups crushed berries
1 package powdered pectin
7 cups sugar
Combine berries and pectin. Bring to boil over high heat. Add sugar, stirring until dissolved. Bring to a rolling boil. Boil for one minute, stirring constantly. Remove from heat. Skim foam, if necessary. Fill hot jars, leaving 1/4 inch headspace. Add lids and process 10 minutes in a water bath.
High altitude instructions
1,001 - 3,000 feet : increase processing time by 5 minutes
3,001 - 6,000 feet : increase processing time by 10 minutes
6,001 - 8,000 feet : increase processing time by 15 minutes
8,001 - 10,000 feet : increase processing time by 20 minutes