Oh, the elusive state of shine in the world of curly hair. Historically, we ladies with curly tresses have more issues with natural shine than our straight-haired sisters because of how our hair catches the light. Straight hair reflects light, giving it a shiny appearance; curly hair refracts, or diffuses, light, making it appear dull and drab. Consequently, girls with curls often turn to shine enhancers to add the additional shine we lack naturally. It is important, however, to understand the differences between the different types and to know how to choose the most appropriate one to ensure good hair health over the long term.
There are three main types of shine enhances: silicone serums, oil serums and glazes.
Everyone is familiar with silicone-based shine serums, which claim to smooth the hair surface and add brilliant shine. Most of these serums, however, consist of non-water soluble silicones, such as dimethicone or dimethiconol, which form an impenetrable barrier on the hair shaft. Any product ingredient which seals the hair shaft shut can be problematic and create issues in the long run. The cuticle of our hair strand is formed like roof tiles to allow penetration of moisture and oxygen into the hair shaft for a reason. Continually coating and sealing the cuticle to prevent it from performing its proper function for a long period of time is not the best route to optimum hair health in the long run.
If you are going to use a shine serum, find one that includes water-soluble silicones, such as dimethicone copolyol or PEG/PPG-manufactured silicones, whenever possible to avoid any potential issues.
Many believe a safer alternative to silicone-based shine serums are oil serums, which are touted as using carrier oils such as jojoba or olive oil to deliver shine and manageability. The vast majority of these products usually also contain some level of non-water soluble silicones in addition to the oils, however, and sometimes in greater quantity than the oils themselves. Additionally, care must be taken when using any type of heat application with any oil-based product as excess heat can literally "fry" a hair shaft coated in oil.
If you would like to use oils for shine, a good approach is to buy a can of olive oil cooking spray (such as Pam®) and use it to spray lightly on your curls (for both shine and frizz control). Be judicious, as you do not want to make yourself oily from using too much. Keeping the spray can at least 10 inches from your hair while spraying will also help to ensure any propellants will dissipate before reaching your hair.
I love clear shine glazes and use them often in my own color work. Glazes are mainly semi- or demi-permanent color treatments with a clear or tinted result. They are different from permanent color in that they only stain the outside of the cuticle, whereas permanent color actually results in a chemical change inside the cortex. Clear glazes add a beautiful dimension and give hair enormous depth and shine.
As a bonus, glazes can help to prevent permanent color from fading since they add another level of "defense" on top of the hair shaft and normally last anywhere from six to 12 weeks, depending on the type of glaze used. Glazes are my preferred method for adding long-lasting shine to hair.