If you make a perfectly level block and try to line it up on one of said cryos, you’ll find that it's impossible to close the gap between the top of the block and the blade. Your options at this point are:
1. Rotate the block upside down. You'll also have to pick up the sections with an upside-down slide so that piece 1 is still on the left side. Or,
2. Melt it down and remake it as a slanted block.
1. Rotate the block upside down. You'll also have to pick up the sections with an upside-down slide so that piece 1 is still on the left side. Or,
2. Melt it down and remake it as a slanted block.
Since you never know which cryos require this, it’s best to just get into the habit of making slanted mounts every single time.
How: When sandwiching the tissue between the heat sink and the disc on the cold bar, angle the mounting slide so that the OCT block is thinner on the side closest to the cryostat wall. It doesn’t need to be steeply slanted, just a subtle slant that you probably won’t be able to see until you take the frozen block off the cold bar.
Be careful not to make the OCT block so thin on one side that it cuts directly into the disc. You won’t be able to get any sections from it and you’ll have to melt it down and start over.
