The first step involves acquiring the necessary materials and proper tools. It is best to get everything prepared before commencing because you are free to progress without unnecessary interruptions.

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).

Next, insert the item of your choice. It shouldn't be something too fragile because the recipient will probably use a nutcracker and may crush through the shell. Make sure the item fits completely within the shell; any protrusion is an indication that you need to find a bigger walnut or a smaller insert.

Instead of having to give an instruction to the recipient that they should open the walnuts, we like to make the gift self explanatory. We usually give the special walnuts along with a nutcracker and to make it clear that these are not ordinary walnuts we ensure that at least one has something sticking out from the base. The base of a walnut has a small hole which is a convenient exit point for some twine or ribbon. It is important that the protruding item doesn't fall out or can be pulled out; We have discovered that a string or ribbon with a knot tied in the walnut end works well. You can tie the other end to the nutcracker. We have provided several ideas for inserts in our design considerations section at the end of this plan.

The final step is the gluing step. Cyanoacrylate-based glue works fantastically: it dries quickly and yields an incredibly strong bond. You only need to be careful not to get any of the glue on your fingers and you'll want to avoid any of the glue dripping out onto the outside of the shell - it dries shiny and it makes the shell unsightly. You also should try to avoid too much glue seeping into the walnut because that could affect whatever you inserted. Don't feel tempted to use large amounts; a small amount along with the appropriate pressure will yield a joint stronger than the walnut shell itself. We usually refrain from applying drops of glue directly from the container because it usually provides too much glue for the application. Put some of the glue on a piece of plastic or glossy magazine (so that it doesn't get soaked up); with a small scrap of paper, sop up some glue and apply it to the gluing surface. After glue application, mate the two walnut shell halves and clamp them together by twisting a rubber band around as many times as necessary to get a snug fit. If some glue squeezes out, you may be able to wipe it away with a damp cloth, but hurry, you won't have much time.

Try this out several times because it takes some practice before you can achieve an invisible joint. We also like to let the glue dry and try opening a few to test the bond: if the shell breaks at the joint, its an indication that you didn't use enough glue or the surfaces weren't mating properly. With some patience and practice and you can achieve strong and invisible joints.

With a little creativity, you can do many things with these walnut shell cases. You can insert a poem, a fortune, movie tickets, or a photo. You can also tear paper-based inserts into several pieces that are put into separate walnut shells: the recipient will have to piece them together. How about good luck charm, a coin, or paper money. If a few people are sharing a special occasion, you can give a bunch of these shells and let them alternate choosing and opening shells. Many photograph developing shops are providing photo-jigsaw-puzzle services. You provide a photo or printed sheet and they return a jigsaw puzzle of the photograph: you can put each individual piece in its own shell. Make sure that the pieces are small enough to fit within your batch of walnuts!

You may want to think about the significance of the act of removing a shell (becoming more open, honest and forthcoming) and tie it in with the poem you include. We made a nutcracker holder made out of oiled walnut wood, then threaded some twine through a drilled hole in the holder. We tied knots at each end of the twine and glued the shells around the knots with half of a poem in each. See the image on the right.

You can give a special stuffed walnut along with a group of ordinary walnuts; the recipient would have to try opening many of them before discovering the unique one. If you do this you may have to experiment with putting some extra weight inside so that the embellished walnut feels real. We have incorporated this concept into our treasure hunt project.

Walnut shells also make a great party favor that your guests will only discover the contents when they return home: it can be as simple as a note reminding them of the gathering. Or for a joke, you can fit an almond or peanut inside (as shown on the right); you'll get some surprising reactions. If you have any additional ideas, please let us know.