Ghostshield sila-tek 3500: our cost-effective, all-in-one primer, densifier and sodium-based hardener. Available in an industry leading, concentrated formula that mixes with water to makes 5 gal. Concentrated and cost-effective: this cost-effective sodium-based densifier is often used before polishing concrete. It also works well as a primer to strengthen and harden concrete and increase the performance of a sealer. When used as a primer it increases adhesion of a top coat sealer up to 25%. Use prior to polishing concrete: easily applied with a sprayer, roller or brush, the 3500 can be used on a variety of poured concrete substrates. Can be used indoors and outdoors but a sealer is recommended to be used in conjunction if concrete will not be polished. A popular choice to prime and harden new and old concrete. Not recommended for: bricks, concrete blocks / cinderblocks, polished or extremely smooth concrete dries clear and natural: provides a flat, natural finish. Treated concrete will not change in appearance, color or texture unless concrete is polished. This dual-function product is mixed with water prior to application and dries within a few hours of application. Once a densifier has been used, you do not need to retreat concrete in the future. Often used prior to polishing concrete to achieve a glossy finish. Color: Clear/ Natural.