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Selecting a smoothing serum for hair is a process of four basic steps, including investigating hair type, hair oiliness and thickness, the serum ingredients, and how the individual wants to use the product. The goal is always to select a serum that effectively coats and controls frizz and flyaways without weighing down the hair or making it look greasy. Consumers should keep in mind that the effectiveness of other hair care products such as conditioners have an effect on the hair and therefore influence which serum works best.
The first step to picking a smoothing serum is to look at the type of hair the user has. Smoothing serums all are designed to control flyaways and increase shine, but they have different formulations based on the structure and condition of the hair strand. For instance, curly hair tends to have a rougher cuticle or outer layer, because the kinks in the hair strand do not allow the scales of protein to sit as flat as they could. This type of hair thus needs a thicker serum designed to combat the resulting dryness and which is more efficient at sealing the strands.
The thickness and oiliness of the hair is a factor in selecting the right smoothing serum, as well. Thicker hair — that is, hair that has a larger diameter — generally does not get weighed down as easily and therefore can handle a slightly thicker or heavier serum. Hair that is fine with a smaller diameter needs a very light product to keep from getting flattened, by comparison. The oilier hair is, the more weight and sealing already are present, so this type of hair also needs a lighter product. Oil does not accumulate as heavily on the ends of hair strands simply because the ends are far away from the oil grands of the scalp, so examining this area can provide a better idea of the formulation or amount of hair serum a person needs.
Next, consider the general ingredients. A smoothing serum falls into one or two categories: silicone or oil-based. Silicone serums are lighter than oil serums in most cases, but this depends on the type of oil a manufacturer uses. The finer or straighter a person's hair, the lighter ingredients she needs. People with sensitive skin or allergies have to check ingredient lists not only to ensure the serum is compatible with the hair, but also to avoid reactions and irritation.
Lastly, look at the way a person wants to use the product. If a person hand-styles her hair the majority of the time and lets it air dry, then a liquid or gel-based serum in a pump container makes the most sense. When a person uses a brush, blow dryer and other heat-based tools to style, however, or if she wants to use the smoothing serum for a finishing glimmer on the hair after styling, sprays are better.