Once canned can you make marmalade firmer?

Yes, you can make canned marmalade firmer by adding additional pectin during the cooking process or by using less liquid in the recipe. If the marmalade is already canned, you can reheat it with more pectin or a thickening agent like cornstarch, but this may alter the texture. Another option is to store the marmalade in the refrigerator, where it may firm up slightly as it cools. Always ensure to follow safe canning practices to avoid spoilage.