What's going on when the pins seem to "disappear"?

[Plainodd]

I've been picking my first lock, a Master Lock #4, and I've unlocked it quite a few times.

I can usually see the first pin by looking inside, but sometimes while raking I'd look in there and see pure blackness. The first pin isn't in the right position being that I cannot unlock it, and it seems like everything disappears until I let loose on the tension a bit and the first pin pops back into place

So, I'm curious as to what's happening to make it appear that way.

[weilawei]

Sounds like you've overset the pin. Both the key and driver pins are wedged up into the upper chamber, with a bit of the key pin sticking down across the shear line. Since you've got tension on the plug, it won't drop back down until you ease up.

On a side note, it's possible to pick things in reverse sometimes. You can overset a pin and then use your pick to lower it to the correct height as you ease off the tension. When it hits the shear line, you re-apply tension.

[Solomon]

I'd say the front pin is oversetting. Or maybe you're oversetting the whole lot

[Plainodd]

Alright, good to know.

Thank you very much.