Let's start by cracking open some walnuts. Opening walnuts is not particularly difficult, but for this project, we need to open them cleanly. It is not critical that we crack the nuts along the border between the two halves, although it is a convenient place for the break. The goal is simply to split the shell into two pieces without damaging any other parts of the shell. Unfortunately, there is no foolproof way to accomplish this.

It turns out that not all walnuts are the same. The easiest way to crack open walnuts is to find suitable walnuts. It seems that older (less fresh) walnuts do best, in fact we just acquired some walnuts that we were able to open simply by twisting the halves apart. Younger, fresher walnuts seem to be much harder to get into, and then not all walnuts react the same to the various cracking techniques. The older walnuts seem to take on the smell of paint and in some places the flavor of these older walnuts is preferred to fresh walnuts. The best thing to do is to buy more walnuts than you need, and test a few different techniques to find out which one works best for your batch.

nutcracker method

Using a nutcracker may seem like the most straightforward method, but ordinary nutcrackers tend to crush walnuts as opposed to providing the clean crack that we are striving for. With a little practice, though, we were able to get a reasonable success rate. The key appears to be a gradual increase in pressure as opposed to a quick squeeze. Increase the force until you hear a crack and then determine if the gap is sufficient enough to pry open the shell (without damaging it) with a screwdriver or similar tool. Prying too hard may damage the edges of the crack; if the shell is giving too much resistance, apply a little more pressure with the nutcracker.

hammer method

Gentle tapping with a hammer or stone often yields good results. Again your success will depend greatly on the batch of walnuts that you are using. While firmly holding a walnut, gently tap on the pointed end (this seems to work best for us). You can increase the strength of the hammer strikes until you hear the crack. Stop immediately and assess the damage, you usually can pry open the walnut with a screwdriver; if not, strike the shell again.

vise method

A benchtop vise is able to provide a gradually increasing amount of pressure which is well-suited to the task at hand. We have had the best results clamping the walnut from end to end and slowly increasing the pressure until the inevitable crack.

bench arbor press method

This is the most elaborate method, but it yielded the most consistent results. Surprisingly, some bench arbor presses are rather inexpensive, but we wouldn't invest in one unless you had a huge batch of walnuts to crack, or have other uses for the tool. We started by cutting a strip of steel and grinded one end to a rounded and relatively sharpened blade. You may want to experiment with alternative shaped blades. After screwing the blade to the ram we used the setup to split the walnuts in half. While we didn't always create cracks where we expected to, this method almost always provided a walnut shell that we could use for this project.

The easiest way to achieve the desired cracks is to find easy-to-open walnuts, otherwise your best bet is some trial and error. Buy several times more walnuts than you intend to use; don't worry though, its not as if the unused and improperly cracked walnuts have to go uneaten! We tried soaking the walnuts in water for varying lengths of time and we determined that there wasn't a significant increase in success. One more tip: once you have the cracked shells, keep them together so you don't have a puzzle to find out which one goes with which one (unless you enjoy the challenge).