How can you make jelly hard?

* Pectin: This is a natural gelling agent found in fruits. The more pectin you use, the firmer your jelly will be.

* Sugar: Sugar helps to extract the pectin from the fruit and also helps to create a gel. The more sugar you use, the firmer your jelly will be.

Here are some tips to ensure your jelly sets properly:

* Use the right amount of pectin: Follow the recipe carefully. Using too much pectin can make your jelly overly firm, while using too little will result in a runny jelly.

* Add enough sugar: Recipes will specify the sugar amount for optimal results.

* Cook the jelly long enough: The pectin needs time to activate and set the jelly.

* Use a good quality pectin: Use a pectin specifically designed for jelly making.

* Test the set: After cooking, you can test the jelly's firmness by placing a small amount on a chilled plate. It should be set enough to hold its shape.

It's important to note that you can't change the firmness of already made jelly. Once set, it will maintain its consistency.

However, if you want a thicker, more firm jelly, you can always add more pectin or sugar to the recipe. Just remember to adjust the recipe accordingly.