There are a number of ways to make ice cream without a machine. Perhaps the easiest is to use a regular freezer and stir at intervals. The fastest is to mix the base with a couple volumes of liquid nitrogen, which gives you ready to eat ice cream in ten seconds.
It's helpful to understand what the ice cream mixing machine does, in order to consider what you need to do to get a suitable product. Consider the clasic hand-cranked sort. The basic idea is that the dashers agitate the ice-cream-to-be, while the can rotates in the ice/salt mixture. The dashers agitate the ice-cream-to-be helps prevent the ice cream from freezing into big crystals of frozen water, and also entrain some air into the frozen mixture, which reduces the density, makes it a bit softer, and probably changes the mouth-texture. Rotating the can keeps the freezing ice/salt mixture in motion, which ensures that the can is always in contact with the coldest part of the mixture; that reduces the amount of time it takes to freeze the mixture. That's good, both because it's faster (less cranking! yeah! eat it sooner!) and because it reduces the production of ice crystals.
With that in mind, here are a few ways to make ice cream without an ice cream machine...
Easiest: Making Ice Cream With Man Power And A Freezer
Putting the bowl in the freezer and stirring every hour or so is easy. Continue this process until the ice cream is frozen to your satisfaction.
Unfortunately, this method doesn't produce terribly good results. It'll tend to have big ice crystals in it, won't freeze as hard as you'd like, and takes a long time.
Making Ice Cream With A Ziplock Bag, Salt, And Ice
- Put a small volume of base in a large Ziplock bag
- Use about a pint or pint and half of base with a two gallon ziplock, which goes nearly flat (so as to maximize the surface area exposed to the ice/salt - squeeze all the air out, too)
- Seal the bag
- Place this bag onto a bed of ice and then cover in more ice/salt
- Let sit for 20 minutes or so, take out of the ice, knead the starting to freeze mixture, put back in the ice for another 20 minutes.
- If you stop before it's solidly frozen, you can put the ice cream in a more elegent container. If you don't, you may have to slice the bag open to get it out.
Making Ice Cream With Liquid Nitrogen
Freezing ice cream as fast as possible gives more and smaller crystals resulting in smoother ice cream. For this reason and the fact that liquid nitrogen can safely be added directly to your ingredients, probably make it the best possible choice to freeze ice cream. However, unless you've got a friendly cryogentics facillity or chemist, it's rather hard to get small volumes of liquid nitrogen.
Liquid nitrogen ice cream is a technique that requires a bit of practice to perfect. You can just dump a whole load in a whole of ice cream base and whisk, but you you get chunks of frozen mix or a giant frozen wad.
The key is to (despite want to achieve quick freezing) take it slowly... take about a few minutes to incorporate the liquid nitro into the mix while keeping the sides of the bowl cool but not painful to the touch, this will prevent the sides from completely freezing over and make the ice cream/sorbet spinnable. For this, you can use a stand mixer with the paddle attachment. If you do it right you will have the smoothest frozen dessert without undesirable lumps of or chunks of frozen stuff.
Making Ice Cream With Dry Ice
If not into nitrogen another fast and easy way is using dry ice. Dry Ice is much easier to find than liquid nitrogen and is just as fun.
Using Dry Ice
- To find dry ice check with a place that refills fire extinguishers and other CO2 bottles like those for kegerators. It's usually around $2 a pound.
- You could also discharge a fire extinguisher into a pillow case to get it.
- Dry ice can be stored in a cooler for 12 hours or so. (No airtight coolers!)
- 3-5 lbs is enough for a batch of ice cream depending on how long you wait to use it.
Fire extinguishers need to have food grade CO2 so it should be safe to add directly to your ingredients as well. The catch is that your ice cream will take on a bunch of CO2 and actually come out carbonated! Kind of funky for typical vanilla but you can make a champagne sorbet that fizzes like champagne in your mouth and people are blown away by the effect!
This method is also really good for tailgaiting. Use the dry ice to keep your coolers cold and then bring a big metal bowl and make ice cream at the game the whole fog thing puts on quite a show.
To avoid the carbonation affect a container with your ingredients can be dipped into a slurry of dry ice and liquid. The ideal liquid will have a freezing point well under -110F like Alcohol or Acetone (be sure that it won't melt your bag if you use one!) This slurry will give you a maximum heat transfer to your container. You'll definitely want gloves for this and any handling of dry ice by the way.