Hot, sticky summer weather most certainly calls for a super-lightweight foundation or tinted moisturizer. I had run out of my beloved DuWop Revolotion Face, but couldn't find a suitable alternative in my beauty closet, so I decided to take matters into my own hands. (A serious bout of insomnia helped, too.)

I began with a bottle of Estee Lauder Resilience Lift Extreme Ultra Firming Makeup SPF 15 in a shade that was a bit too dark for my skin. I had received it as a sample and had been using it sparingly or mixed with moisturizer, so some had been used up and there was some space in the bottle.

So I set out to concoct a custom tinted moisturizer right there in the bottle; in the past I had mixed various things on the back of my hand before applying, but this time I wanted a ready-made dose.

To the foundation I added several pumps of Bobbi Brown Oil Control Lotion SPF 15, which keeps oil at bay and maintains the SPF level of my little concoction. Perfect for summer, right? Adding it lightened up the foundation in both shade and weight, bringing it closer to tinted moisturizer status.

And a finishing touch, I poured in a few drops of Stila All Over Shimmer Liquid Luminizer in #3, a pale luminous gold. I wanted to add a hint of dewiness and luminosity without looking oily, so a touch of this favorite Stila product did just the trick (and combined with the BB Oil Control Lotion, ensured that the level of dewiness was in my control, not that of the weather).

The initial result was a swirly, goopy mess - a mess in a bottle, if you will - but after some vigorous stirring and shaking, I finally achieved what I had set out for - a lightweight, moisturizing, luminous tinted moisturizer with sun protection. Voila! And since I mixed it myself to my own specifications, it's actually far superior to most tinted moisturizers I've used in the past.

Chances are you already have some SPF moisturizer and some sort of liquid shimmer product in your arsenal, so if you're stuck with a too-dark or too-heavy foundation, mix it up!