I am a huge advocate of daily SPF, particularly for the face. It the simplest and most effective way to ward off premature ageing and of course a preventive method against skin cancer. One thing I have noticed is that there is next to no education, be it on the back of a box or via a brand's website in regards to application and removal of facial SPF. In hopefully the least patronising way possible let me shed some light on how to get the most from your facial SPF and how to remove the product, to prevent blocked pores and of course blemishes.
When I first began reading up on facial SPF I thought any old product would do; to an extent that is true, you don't need to spend a small fortune on a great formula, all you need is a product that offers a high SPF rating as well as both UVA and UVB protection. The higher the SPF factor, the longer the product will protect the skin and the longer you can go between applications. For example, if on average takes you 10 minutes to burn in the sun, a factor 15 would protect you for around 150 minutes or two and half hours. The same calculation can be applied for any SPF rating - using the same maths, a factor 30 would protect for 5 hours and a factor 50 for just over 8 hours.
With foundation, primers and more now containing SPF you may be tempted to skip a separate sun screen, as great as such addition is we simply don't apply enough foundation (liquid, powder or even primer) in terms of volume of product, or regularly enough to gain adequate protection. For instance did you know that to fully protect a small area such as the face you need 2ml of SPF? I didn't either and for sake of scale, that is around the size of a lid from a standard water bottle.I seldom if ever apply that quantity of foundation to my face so that alone is a problem. If you do skimp, for instance say you apply closer to 1ml daily then you half your sun protection - i.e an SPF of 30 will reduce to a 15 and so forth, something no cosmetic product label mentions.
When I first began using facial SPF I had no real idea when you should apply the product, I knew it had to go onto the skin before foundation but other than that it was complete guess work. Apparently facial SPF should be applied after your daily moisturiser and before you apply any make up. I would also suggest that you give the SPF a few moments to properly absorb and then apply foundation et al. In general it is recommend that you apply any form of sun screen 20 minutes before stepping outside and re-apply should you go into water.
As so many have commented in the past, the main reason for avoiding facial SPF is skin irritation and of course blocked pores and blemishes. I do personally believe that in the last few years textures have become lighter and as a result far more comfortable to apply; not to mention less prone to skin aggravation. To fully remove SPF I can not recommend using an oil based cleanser enough, the oily texture helps to quickly break down the tough SPF.
And that my friends is all I know about facial SPF, feel free to add to the above advice in the comment section and/or tell me your favourite facial SPF!