Cream of tartar

Good question lilyfield.

Two reasons, Firstly I knew it was quite old and possibly might have lost quality as far as a raising component (I had mixed it with baking soda) but also I was not expecting the replacement to be as expensive as it was. I certainly learned some lessons.

I should have not been so hasty however I did scrape enough for the teaspoon of the cream of tartar I needed to go with the baking soda. The baking didn't rise as much as I expected.

I should check the lids on all my jars for their being closed or loose more often.
I wonder though how long should we keep stuff in the back of cupboards.
Recently I threw out some ancient treacle. I think this is the only tin I've bought and I did that in the early 1970s.
Spices would have I imagine a time when they aren't as good as they were once. I don't know how long I should keep these for though.
I often end up throwing old stored grains out as I can these do show signs of being less than best.

Went to use this on Thursday but it had gone hard so threw it out as it was very old. I'd bought a big container of it ages ago. Lessons learned - must ensure containers have properly secured lids because purchased a smaller container at Countdown this morning to replace it. For 100 gms $5.69 (smaller than the one thrown out). Also it clearly isn't a good idea to purchase more than a little at a time given I threw out more than I purchased today.
That seems to me a very expensive ingredient that is used only a little but nevertheless is a fairly straightforward 'chemical' ingredient.

you can get it a wee bit cheaper from pak n sav and much better quality, its only about 100 grams but i would rather smaller than larger so yes it will be more expensive for you, a lesson learnt

So why did you throw it out instead of hammering it or pulsing in a spice mill

It does not go off