37 20/20 gems vaal'd, none hit L21

Is the vaal orb broke? Does it actually do anything beneficial to skill gems anymore?

Three out of 37 bumped in quality but not a single gem jumped level. Four lost a level and 21 out of 30 just corrupted.

This is the second large batch of 20/20 gems I've vaal'd and that's about the same results I got with the last batch. What are the percentages on these wastes of time, space, and effort?

Its about a 1/6 or 1/7 or so for a 21 gem so unlucky but not way out there statistics wise.

If all vaal outcomes have the same chance it is

1/4 do nothing
1/4 change to vaal gem variant (if exist)
1/4 +/- one level
1/4 +/- quality

Means your chance for +1 level is 1/8 (= 1:7).

Read wiki.

RNG doesnt like You.

I havent found one t17 map.

(My mistake, I misread the post, 0/37 is a 0.71% chance, so that is an unusually bad run, particularly combined with a low amount of +qual rolls. Going to happen sometimes though.)

What gem are you trying to upgrade? Does it have a vaal version?

I believe what Jerexil has posted is correct for single corrupting by vaal orbs, from the wiki.

So your results seem fairly typical to the underlying probabilities. With binomial probability the chance of getting 3 or less +1 results out of 37 trials, at a probability of 1/8 is 30.4%. The most likely result would be 4/37. 3/37 is the third most likely result after 4 and 5. The average result is 37/8=4.625. So based on all of this your, results are a bit worse than expected if you are trying to get +1's, but very typical.

Not sure if you have created/found these 20/20 yourself or trading for testing/gambling/efficiency over buying a 21/20, but double corrupting is an option that will give you bit of an increased chance each time at a 21. It's less than double I believe. I think there is a chance it can roll up/down, for no result, and I think the rolls are conditional, but I'm not certain on the specifics of the process. I haven't come across a definitive answer of this before, though i've seen people do testing, and the results are fairly in line doing 2 vaal orbs, with some outcomes not possible, like no 22/20. Obviously this is a much more expensive or time consuming process to buy or farm out, but you will also have a chance at more powerful outcomes as well, like 21/23 and 21/vaal if possible for that gem.

This was quite a while ago but I was farming to sell them so I know there was a market for level 21 gems on them all. There were several different ones. Hypothermia was one I'm pretty sure.