I'm not expert other than playing with many different chalks...I use BD almost exclusively, and Masters if I'm out of BD. The question I would like to ask is: What if it isn't a matter of formulas changing, but of age? What if older chalk just applies and "plays" better simply due to the aging process?
Just curious.
Chalk that "plays well" grabs the cue ball. I think that this comes down to ingredients, the proportions of the ingredients and possibly the process of making it as well. I think that chalk that "applies well" goes on in a nice even, complete coat and not caky. I think this comes down to ingredients, moisture content, hardness and to whatever extent moisture content affects hardness.
That's how I'm looking at it at this point, subject to change because I'm still trying to figure it out myself.
I think the pre-flag Master is better because of some kind of actual difference in the formulation. The batches that I have had actually do not apply as well as I would like because it's a bit on the hard/dry side. You have to work it a bit. But it has the grittiness that today's Master chalk does not have and that is why it's better, in my opinion. I'm hoping that making it absorb more moisture would make it better in terms of applying it. If making it more moist just changes it into being exactly like a batch of new Master, then I'd have to confess I was wrong. I don't think that would happen though. I have baked today's Master to dry it out and make it apply better (it's starts out too caky). After doing this, I liked the way it applied, but it didn't improve the performance in terms of grabbing the cue ball.
As far as I can guess the aging process is going to primarily affect moisture content, and even that seems to be dependent on the environment that it's stored in - seems to be the lesson from this thread. If it could affect other aspects of the chalk, I don't think so, but would be open to other ideas about that.
I tried some cheap chalk I got on ebay recently. The seller said flat out it was made in China. It coated nice and evenly. It looked good going on. And it seemed nice and gritty too. But then it didn't stick to the tip. I mean one shot and it was gone. Not only that, it caused the tip to glaze very quickly. I don't know the mechanisms behind it all, but bottom line is that it was just crap chalk.
Right now I think bad chalk is bad chalk and good chalk is good chalk and aging it isn't going to make it better or worse other than moisture content which would affect how well it applies and therefore maybe only slightly how well it plays.
I recall that I tried NIR once. It was soft and messy. I gave up on it thinking, I'll find something better. But my recollection is that it coated well. My criteria for chalk is this...
1. Plays well
2. Applies well
3. Not messy
4. Readily available
5. Reasonably priced
Now that I have tried so many different brands of chalk, it just seems like there's nothing out there that meets all my criteria. So I'm re-thinking the order of priorities of the above list. I have ordered more NIR to try it again. If it plays well, I might just learn to live with the messy-ness or try baking it to see if that'll help (I hadn't gotten into the idea of baking chalk at that time yet).