SoluGreen is double screened, creating a very uniform SGN (approximately 100) with the lowest heavy metal content. We use only virgin oleum sulfuric acid in the manufacturing process, which makes our product extremely soluble as compared to cheaper spent or merchant grade sulfuric acid products. That is why SoluGreen has the lowest heavy metal content in the industry. Organics are removed before SoluGreen crystallizes, resulting in a non foaming product.