CONVECTION versus CONDUCTION
Always a good debate about which is better. Convection or conduction. I think the answer is a resounding YES. By and large I have leaned into making ANVIL as convection oriented as possible but there are obviously times when a conduction bump might yield better results. I’m thinking concentrates, kief, or sometimes just a big badass bong rip. Thankfully Whiff has been documenting how his bowls have been aging and they tell a story totally in line with our ANVIL design objectives.
A look at these well used Anvil herb chambers gives one a pretty clear picture of what’s going on. We aren’t “tempering” the herb chambers in the classic Katana sense but they are being tempered never-the-less by the repeated heating cycles. Anvil’s herb chambers are mechanically connected to the CopperCore oven only through the 4-start threads. Apart from that direct connection the herb chambers “float” centrally in the oven surrounded by a 0.014” ring-shaped air gap. The temperature sensing SNAP discs sit below the slots/holes in a pocket tucked in behind the threads. The ultimate temperature the outer CopperCore oven achieves at the time of the SNAP is of course determined by where on the oven we heat it. Importantly the herb chambers always SNAP at the same temperature so darker roasts, or estratto, are achieved by tricking the SNAPs. This is done in the ANVIL by heating further up the oven effectively storing more total energy by charging up the CopperBlock thermal reservoir. A proper detailed discussion of the thermal propagation and storage in the CopperCore oven is best left for another post.
Tonight’s discussion is focused on recognizing the clearly visible temperature difference at the time of SNAP of the terp chambers at left, pale yellow/silver, versus the helix chamberat right, golden straw, while the threads of both are almost brown.
What accounts for these differences? The convection biased “terp" chambers at left are significantly isolated by the large air intake slot. The dimensions of this slot are much larger than required exclusively for airflow but are extended to make an impenetrable thermal bridge. The heat transmitted through the threads cannot propagate up into the herb chamber because of the almost full circumferential air gap. Keeping the material at this lower temperature before draw prevents the most volatile flavour terpenes from boiling away. A full flavour full extraction hit results.
In contrast the higher temperatures achieved in the conduction biased HELIX bowl are clearly evidenced by the golden straw colour of the herb chamber. The additional heat builds up in the HELIX through two paths. First the air slots have been replaced with much smaller holes maximizing the metal conduction from the threads up into the material. The second heating factor results from the peaks of the helical grooves coming right up to the inside of the CopperCore oven inner wall reducing the isolation air gap to only 0.002”. The combination of these two effects has proven effective in biasing the Beta HELIX to conduction but we were unimpressed with how much effort it is to draw. Nobody digs those light headed “milkshake” moments. We are currently working on a new version of the HELIX with deeper grooves and short vertical slots that we hope will preserve the enhanced conduction characteristics we’ve achieved so far without having to burst a blood vessel to get a good rip.