The first thing to point out is that the single dot and line had almost no air bubbles, but they did not spread across the entire CPU. Even doubling the size of the dot still did not cover the entire CPU as the majority of the extra thermal paste simple squirted out the sides. Using three lines instead of one helped with coverage, but resulted in more air bubbles.
Both roughly and smoothly spreading the thermal paste across the CPU had great coverage, but resulted in quite a few small air bubbles. These air bubbles are tiny compared to the circle and spiral shapes and likely to have a minimal effect on performance, but they are definitely present. Spreading the thermal paste perfectly should result in fewer air bubbles, but in our experience it is impossible to get it 100% perfect.
Surprisingly, the X shape resulted in the best overall spread with great coverage and very few air bubbles. This surprised us a bit, but makes perfect sense when you think about it. The X shape allows the paste to spread equally across the CPU, and since the spread is from the inside out, the shape helps prevent air pockets from becoming trapped.
