I really hope you are feeling much, much better. I saw a comment from you awhile back, but not much since. Here’s hoping you’re feeling great, and just too busy catching up on fun things to comment lately!

That is why it is so helpful when you share the information that you do based on your personal experiences and testing. It makes the overall experience better for all clayers. Which means the end result will be better end products out there. Important, since we are pushing the polymer clay medium out of the Kid Toy category and into the Art Medium category.

Thanks again for all input you share here at the blog. It is appreciated by many!

Baking time also depends somewhat on how well your oven holds its temperature, i.e. whether it stays very close to the designated temperature (or at least to a known temperature), or whether it cools down significantly before heating up again. I have two different ovens that I use for polymer clay, and both hold their temperature pretty well. One of them (a “big”, kitchen-type oven) has a 5C temperature variation from minimum to maximum throughout its heating cycle, i.e. if I set 150C, the oven heats to 152C, the temperature drops very slowly back to a minimum of 147C, and then it starts heating up again. The other is actually a convection microwave that I use in convection mode, and it hardly has any temperature variation at all, i.e. the oven thermometer needle doesn’t move noticeably at all once the oven is up to temperature. If using an oven with a larger temperature variation (10C or more would not be uncommon from what I’ve seen) I’d probably bake for slightly longer to ensure that sufficient time was spent at the “proper” curing temperature.

It’s interesting what you say about your Ks and Js. I know that what I described works for my stocks of Kato, and all of it is of known formulation, but it was just a guess. I have had a couple of blocks of Kato White that were so soft that I had to leach them, and they were definitely old-formula because I bought them well before the new formula was even talked about. So I don’t think the fact that a K block was soft necessarily means it wasn’t the old formula (sorry for that horrible sentence!), but I’d agree that it would be very unusual! In any case, the Ks and Js are the ONLY visible difference between my old-formula and new-formula Kato, and if that isn’t a reliable indicator after all we’re stuffed. I’ll see if I can find out anything further…

Also, I just worked with some Kato and one that started with K was nice and soft. One with J wasn’t too crumbly, but not as soft as K. Then I had one where the number was no longer discernable and it was very crumbly and required clay softener for get it to hold together. Bottom line, I’m not really sure that those K’s and J’s mean anything as far as formulation.

My really old stocks of the formulation that used phthalates all have batch numbers starting with IKPCH.

My stocks of the phthalate-free formulation that replaced it all have batch numbers starting with K.

And known-to-be new-formula Kato that I have (or have seen) has batch numbers starting with J.

The batch number — or the number I’m talking about, in any case — is printed on the front of the 2oz/56g packs in a small font at the bottom right. On 12.5oz/354g packs it’s printed underneath the barcode. And on old 3oz/84g packs it’s printed either underneath or to the left of the barcode.

I’m still testing the new formula, and while I personally definitely prefer the old one, the new formula is much better than I expected, and I think most people will prefer it. I might write more about its characteristics later…

What we get from other places, I guess, could be either old or new.