Adding clam shells or tarts can be extremely easy, and, in many instances, you can use your existing wax formula and these products can then double as a way for you to send samples of what your fragrances smell like.
Ideally, the best wax to use for making tarts and clam shell melts is the CBL-129. It has excellent cold fragrance throw and will release very nice from the clam shell or the tart mold. You can use a low shrink wax but they do not release as well from the molds and soy can be brittle at times getting the wax out without breaking.
If using a wax like CBL-129 or a paraffin wax take the product up to around 140°F. With soy you will only need to take the wax up to around 120°F or so.
When your wax reaches the desired temperatures add your dye. With soy it will be easier to use liquid dyes because they will not have to melt like the color blocks.
Add your fragrance. In most instances, since you want to deliver great fragrance throw with a small cube you should be closer to 7-9% fragrance which works out to about 1.25-1.85 ounce per pound of wax. Again a reason to use the CBL-129 is that it will hold that much fragrance.
Step 4 (alternative)
If you wanted to make tarts you should heat the wax close to 150°F and then choose the mold you want to pour into. The Floating candle mold M-112 is one of the most popular choices but there are many other choices like hearts, ducks, ships and others. In addition soap molds can also be used for making tarts.
The nice thing about the clam shells mold is the packing. After pouring the only handling required is closing and applying a label. The clam shell also has a "peg hole" - making it easy to display on any retail location. These products are also a great way to use up your extra wax and maximize your wax yield.