min-maxed toner becoming a moisturizing gel (which I'm still very much enjoying) and probably saw this picture of it in a Pyrex jug. Don't leave your products in a container like that for too long before bottling!
Evaporation tends not to be our friend in situations like these. Leaving the product in an uncovered, wide mouthed container like this leaves our products susceptible to losing a lot of water in a short period of time. The warmer the room, the more water loss we'll see. A product like this, one that's high in water content, can lose a ton of water in a very short period of time - even in our darn it the furnace is broken and it's snowing outside so it's only 16˚C or 62˚F in the house right now temperature this week, I went from having about 91 ml of product to 85 in two days!
You could use this to your advantage - if you have a bubble bath, body wash, shampoo, or other surfactant mix that needs some thickening, you can use the power of evaporation to reduce the amount of water in the product over time - but then you leave the product open to contamination (check out this post on contamination and packaging), not to mention things like bugs or particles from the air dropping into it! (And when I say bugs, I don't mean little ones like bacteria or fungus, but big ones like flies! These little creatures seem to get curious in my workshop at night, and I've found all kinds of weird things in my unused Pyrex jugs when I reach for them! Yuk!)
Having said that, a larger surface area can be your friend when you're heating your oil phase because we're not as concerned with evaporation when it comes to oils, butters, esters, and so on. Depending upon the ambient air temperature, using a larger, flatter container in your double boiler means you can mix in those larger chunks of butters without removing the product from the heat! (If it's really cold in your workshop, a larger surface means this has time to cool when the temperature is very low, so follow this advice only if you're in a reasonably heated room! I've had BTMS-50 cooling on the sides of my container while the liquid under the surface is at 70˚C!)
And if you ever feel like getting me a present, a set of 250 ml and 500 ml Erlenmeyer flasks would be a welcome gift indeed!