Given Brandon's answer to a block of Cheese stopping a shardblade, how does the last clap work?
So, I'll admit, I've been considering the cheese question since it was asked.
I'm not sure if it has to be cheese. But any object that is sufficiently thick but also sufficiently pliable that it's going to press down on the blade while it's cutting IS going to create drag on the blade.
The Blade does, by necessity of my understanding of the relevant physics, need to be able to vaporize a tiny bit of matter into Investiture while cutting, in order to create space for the Blade to continue to slide through. This is related to why it doesn't cut things with souls.
At the same time, I'm not convinced that this is relevant to the actual question being asked. I think that I have to relent that, with a sufficiently large block of cheese and a Shardbearer trying to cut lengthwise through it, the drag produced on the flat of the blade is going to tire the Shardbearer. Making cheese legitimately more difficult to cut through than stone or metal. And a big enough block of cheese might stop the slice straight up, because the weight placed on the blade will be pretty heavy.
That said, the top replies to this thread are pretty relevant, and are correctly explaining the mechanics of the situation. There is this little "shield of vaporization" around a Blade while it cuts, so a thinner Blade (like Szeth's Honorblade) might not have this drawback at all. It depends on how far back the shield of vaporization extends, and how thick the blade is.
My current instinct says that wider blades would be stopped by this, and so those of you planning to make ten-foot-thick walls of cheese to stop an invading Shardbearer can continue in your...endeavors.
Remember, kids, keep your Shardblade thin for actual combat (for multiple reasons.) Only make the big showy forms when you're trying to look intimidating. (With a nod to the fact that a thick blade does tend to be better for getting through Shardplate, giving you more mass to hit with. Choose Adolin's Blade for Shardplate Duels. Szeth/Jezrien's Honorblade for cheese.)