Are the actual in game numbers for the effects of the gums published anywhere?
I know a special gum increases the chance of getting a special boon (thought it doesn’t always feel like it 
), and adding a second does something(?), supposedly increase the chances again.
But what are the base odds, and what do the gums change that to?
Is the second gum supposed to increase the chance by the same amount as the first?
Just from forging last few days:
I completed several forging sessions on 3 and 4 gums of the same type, and I would still get a different type of boon on the first slot every now and again (actually, it was close to half/half situation).
I finished 12 forging sessions using 6 gums of chosen type then. I always got a boon of the same type as the gum on the first slot. On the second slot, I got a different type of boon 2 times (most likely because there was only 1 boon of the wanted type available).
I had a few sessions where I suspected only 2 boons of the wanted type were available, and I didn’t even get the 3rd boon (the 2 boons I got kept leveling up instead).
So, getting to 6 gums of the same type already bumps your chances a lot and significantly minimizes unwanted occurrences.
can’t tell for sure, but doesn’t seem to be the case
the idea seem to be that there is always a chance to fail the roll on the wanted type of boon
But that is a lot of gums to use!
And let’s say you are aiming for devastating damage, you would be increasing your chances of hitting hard hitter by the same amount…
I know using more gums increases your chance of hitting one of the boons tied to that gum, I just wondered if the actual game data was know in this area 
Like we know the drop rate chances on blocks.
This tool is supposed to have relatively accurate chance calculations, but I don’t know where they got their data. https://boundless.mayumi.fi/forgeSimulator/
yes, it only increases chances of getting boons from chosen category and doesn’t help with random factor when getting different boons within that category
no tools available to change that
actual % numbers for stacked gums would have to be extracted form large number of sessions to be considered as true-ish
Maybe there is someone with some data out there?
I think that was from mass testing on the forge in testing.
You would hope that the forge in testing is exactly the same as in live, but I have asked that question before but got no ‘official’ response!
I have moved back to one gum when aiming for aoe and damage, it seems to be not a million miles away from multiple gums in getting me what I want. And the savings on gums and vigour have helped.
Correct, maybe @Mayumichi can give you details of exactly how she tested it but I’m confident she would have tested this a sufficient number of times to get a fairly accurate probability increase per gum applied.
I see absolutely no reason why the forge would be any different in testing and from the few times I have used it in testing I’ve seen no evidence to suggest it is.
Personally, if I have vigor to spare then I use more gums, even a small increase in probability is an increase.
It’s a random selection from a weighted list of boons. By default each boon has a weight of 1, gums add 10 to the weight of boons it targets. The number 10 was an educated guess backed up by some real tests as well by @Tonezone in this thread
From personal experience of mass forging it seems accurate. I also got compliments from James about the simulator so it kind of endorses that it’s correct, even though he didn’t outright confirm the math. Should’ve asked now that I think about it 
I had forgotten I had taken (a small) part in that conversation!
This post is of most interest to me:
Particularly the part where it shows that adding a second special gum only increases the chance of hitting aoe by 5%.
Extrapolating from that adding a 3rd gum increases the chance of hitting aoe by less than 2% on top of that.
1 gum 38%
2 gums 43%
3 gums 44.9%
This is for gums that have 2 targeted boons.
Once I have the boons that I am looking for, then I will use two gums, or if the gum only has one targeted boon, ie lightness - busy bee.
That’s essentially my philosophy also. But if I have spare vigor throughout the process then I will spam more gums just to reduce the chance of boon points going to the wrong boons. For instance if I have AOE 4 and damage 8 already with plenty of vigor to spare then I will use 4 or 5 lightness gums to ensure that all the remaining points go to busy bee and none are wasted elsewhere. Gums cost around 2-5c each to craft so I ignore the price of them.
There are a few variables to the exact chances, the forge simulator shows the exact chances on the boon tooltips.
On a hammer the chances of hitting aoe
0 gums = 10%
1 special gum = 36.7%
2 special gums = 42.0%
3 special gums = 44.3%
4 special gums = 45.6%
5 special gums = 46.4%
Thinking about this a little further, in regards to 2 boon gums.
If I think about in terms of boons that I want rather than just a single specific boon, I am aiming for:
Aoe
Damage
Speed
Using this table:
The chances of hitting a boon I want with a single gum is 44% (aoe 38+dam 3+ speed 3)
With 2 gums:
It’s 47% to hit a boon I want (aoe 43+dam 2+ speed 2).
I assume it will be similar with your more accurate numbers on the simulator.
Pretty close yes. Those tables are missing the liquid breaker boon so it reduces the chances a tiny bit.