Cham does not make a sunscreen. There is nothing to sell at the end of this article, which is worth saying at the start, because sunscreen advice is usually written by someone with a bottle to move.
It is also the step that decides whether everything else in a routine compounds or just holds even. Pigment work in particular runs directly against daylight: every ingredient that slows melanin production is working on a process that sunlight restarts each morning. Get this step right and the rest gets easier. Skip it and the rest is mostly maintenance.
What the numbers on the bottle mean
SPF measures protection against UVB, the wavelength that burns. It is a ratio, not a score out of a hundred. A rating describes how much longer skin takes to redden under a controlled lab dose compared with bare skin.
Two things follow from that. The first is that the difference between a high rating and a very high one is smaller than the numbers suggest, because the scale flattens as it climbs. The second matters more: the lab dose is considerably more product than almost anyone applies. Most people get a fraction of the protection printed on the label, not because the label is wrong but because the application is thinner than the test.
PA ratings, and the European equivalent, describe UVA protection. UVA does not burn. It penetrates deeper, contributes to photoageing, and drives pigment responses. For anyone thinking about tone and dark marks, this is the rating that matters more, and it is the one most people never look at. More plus signs is more UVA protection.
A sunscreen that covers both is usually labelled broad spectrum. If it only carries an SPF number and nothing about UVA, it is doing half the job.
How much, and this is the part that fails
Under-application is the single most common problem, and it is invisible. The product feels applied. It is simply too thin to behave like the label.
The usual heuristic is two fingers: squeeze a line of sunscreen along the length of your index and middle fingers, and use that for face and neck together. It will feel like more than you expect. That is the point.
If your sunscreen is a fluid rather than a cream, measure it by volume instead: roughly a generous coin-sized pool in the palm. Either way, aim high. The failure mode of too much sunscreen is a white cast and a shiny hour. The failure mode of too little is that you believed you were protected.
Apply it in sections rather than rubbing one blob across the whole face, which is how coverage ends up uneven.
The places people miss
Every one of these is somewhere pigment tends to show up later.
The tops of the ears go uncovered almost universally, as do the hairline and any parting. Most people stop short at the eyelids and skip the strip directly under the eye. The sides and back of the neck get missed because you cannot see them while applying, and the upper chest gets missed whenever it is uncovered. The backs of the hands age visibly and receive almost no protection from anyone. Lips need their own product with an SPF in it, since sunscreen is unpleasant there and will not stay put.
Where it goes in the routine
Sunscreen is the last leave-on step of the morning. After serum, after moisturiser, before makeup.
This answers the question people most often ask about it. Moisturiser first, then sunscreen. A sunscreen applied under a cream gets diluted and disturbed by the layer going on top of it, and the film it forms is what does the work. If you are using a serum and a cream, the order runs thinnest to thickest, and then sunscreen sits over all of it.
Give it a minute or two to settle before makeup. Not because it needs to set chemically, but because applying base over a wet film smears both.
Reapplication, realistically
The standard advice is every two hours of sun exposure, and the reason is real: sunscreen degrades with light, and it comes off on hands, phones, sweat and towels.
The honest version is that reapplication is easy at the beach and hard at a desk. A few things that help. If you are indoors and away from windows for most of the day, a single morning application is doing more than the rule implies, and one careful reapplication before an evening commute matters more than three anxious ones. If you are outdoors, reapply properly rather than smearing a thin layer over the old one. Over makeup, a stick or a powder with an SPF is a compromise rather than a replacement, and it is better than nothing.
Anyone who tells you they reapply perfectly every two hours is either outdoors for a living or not being straight with you.
The questions that come up
Do I need it indoors? UVA passes through window glass. UVB largely does not. So a seat by a window is a real exposure and a windowless room is not much of one. Screens are not a meaningful source, whatever the blue-light marketing suggests. If your day is genuinely indoors and away from glass, the case for sunscreen is weaker, and that is an honest thing to say rather than a reason to skip it on the days you do step out.
On cloudy days? Cloud reduces UVB more than it reduces UVA. The burn risk drops and the pigment-driving exposure much less so. Overcast is not shade.
Can I use sunscreen at night? There is no reason to. It is not harmful, it is simply doing nothing after dark, and it is a heavier film than most skin wants through the night. Use a moisturiser instead.
Will sunscreen remove a tan? No. It prevents further pigment from being triggered. A tan is your skin responding to exposure and it fades on its own once the exposure stops. Sunscreen is what lets it fade without being topped up.
Does it stop vitamin D? Real-world sunscreen use has not been shown to cause deficiency, largely because nobody applies it thoroughly enough or often enough to block synthesis completely. If you are concerned, diet and supplementation are the sensible route rather than deliberate unprotected exposure.
When this is not enough
Sunscreen is one layer of sun protection and it is the weakest of the three. Shade and clothing outperform it comfortably. A hat with a brim does more for your face at midday than any bottle, and it does not wear off.
If your skin reacts to chemical filters, mineral formulations based on zinc oxide or titanium dioxide are the usual alternative, and they tend to be better tolerated on sensitised or compromised skin. They are also more likely to leave a cast, which is a genuine trade-off rather than a failing.
If you are using a prescription retinoid or acid, sun sensitivity is higher and this stops being optional.
Infants under six months are usually kept out of direct sun rather than covered in sunscreen. That is a paediatric question, not a skincare one.
And if a patch of skin is changing in a way the rest is not, no sun protection routine answers that. A doctor does.
Where this sits in a Cham routine
Everything Cham makes is a step underneath this one. The face mask works on pigment production, the serum and cream work on hydration, barrier and tone, and all of them are working against daylight unless something is filtering it.
That is the whole argument for a product we do not sell. What brightening can honestly do depends on it more than on any active in the bottle.
