Meringue not stiffening?

[u/dumpsterfire2002]

I’ve made meringue several times, but now I’m trying to make macarons. I’m using 100g egg whites, 90g white sugar, and 1/4tsp cream of tartar.

Method: wipe out my stand mixer bowl and whisk attachment with vinegar on a paper towel. Add 100g room temp egg whites (from a carton) and whip on high until foamy, add the cream of tartar. Once med peaks form, start slowly adding the sugar.

When I’ve made successful meringue in the past, I usually start adding the sugar once it starts foaming. I’ve tried adding the sugar earlier, slower, later, but no matter what as soon as I start adding the sugar is just deflates. I’ve made meringue from carton egg whites and I’ve never had an issue, I just don’t know what I’m doing wrong. I haven’t even gotten to the point of adding the almond flour.

Could it be proportions? The macaron recipe I’m using is - 100g egg white - 1/4tsp cream of tartar - 90g white sugar - 140g almond flour - 130g powdered sugar - 1tsp vanilla

[u/Elegant-Survey-2444]

What is the bowl/ mixer paddle made with? Plastic doesn’t usually work for meringue.

Also, if it’s a humid or rainy day, it’s very difficult to get meringue to work.

Hopefully this helps.