Gemma Labs is raising cash to support increasing demand for its Gemmist custom shampoo service. Gemma Labs spun out of Pioneer Square Labs’ startup studio more than two years ago and raised $3.5 million in April. Gemma Labs uses in-house scientists to concoct special shampoos for individual customers, based on surveys they take that assess individual hair and scalp needs, in addition to seasonal factors. Prices per shampoo or conditioner bottle start at $18 for 8 ounces; Gemma Labs also sells a $25 scalp balancing bar. Gemma Labs will use the fresh cash to roll out new products.