Don't buy it.
I've been trying heat protectant sprays for the last few months. They can be great for protecting your hair from heat damage from hair dryers, flat irons and curling wands, and some can also protect your hair from damaging UV rays, which is particularly good if you colour your hair. In addition, they can add shine, fight frizz and help your hair hold its style.
According to the Rusk website the Thermal Str8 Protective Flat Iron Spray is a humidity-resistant styling spray that penetrates hair, infusing conditioning and controlling agents like argan oil and Thermplex to seal the cuticle, eliminate frizz, precent curl reversion, and protect styles from environmental elements. Conditions and protects the hair internally and externally while smoothing and enhancing shine.
This product is designed just to protect your hair from using a flat iron, not from using a hair dryer, and that seems a bit odd, since usually you need to use a hair dryer before using a flat iron, unless you have time to let your hair air dry after washing it. But the Str8 Protective Flat Iron Spray needs to be used on dry hair because it's incredibly sticky. Holding the can 6-8 inches from your hair is the recommended application technique and in doing so, presumably the amount you end up with on your hair is the correct amount.
I tried a few times and each time, the spray went on heavily, coating my hair with stickiness. I used a brush to comb it through, both to make sure it was on evenly and to try to minimize the stickiness. I thought perhaps the texture of my hair would improve after I used my flat iron, but that was not the case. Running the flat iron over one section of hair after applying the spray created a shiny, smooth, but stiff and crispy piece of hair. I ran my brush through it and this softened the stiffness considerably, making my hair look like actual hair again, but the brush dragged through my hair. The stickiness did not go away, even with repeated brushing.
On the plus side, it did make my hair shiny and added to the straightening effect. I assume that it protected my hair as well, since it seemed to form a seal around my hair with the application of the heat from the flat iron. But the incredible stickiness is horrible and does not go away. Running my fingers through my hair throughout the day resulted in snags and tangles. I guess if no one, including you, touches your hair after you've used this, it's all good, but who wants hair like that? There's a stiffness and a frizz at the ends of my hair as well after using this spray.
I was shocked how terrible this product performs. Especially since there are multiple heat protectant products that perform beautifully.
This one, TRESemme Thermal Creations Heat Tamer Spray is a favourite and it can often be found for sale. I picked up a bottle for $4 recently.
There's no added weight, but it leaves my hair silky, glossy and soft. The lock button on the pump is a nice feature too.
This one too - L'Oreal's Color Radiance Dual Protect Spray - is often on sale. Drugstore brands FTW! It protects your hair from styling tool heat as well as from UV rays, which is great if you colour your hair.
For me, it's a runner-up to the TRESemme Thermal Creations Heat Tamer Spray, but it's a solid project and I don't hesitate to recommend this one as well to you.
Just trust me on the Rusk stuff. Don't be tempted. It's appallingly bad stuff.