About RainCoat® Clear Water Repellent (Oil Base) Use to protect new or weathered wood from water damage, including splitting and warping caused by water absorption. Especially suited for new, unseasoned pressure-treated lumber. Use as a final finish or water repellent primer under an oil-base paint or stain. 100% clear, oil finish reveals original wood color and allows wood to gray naturally. Long-term water repellency exceeds Federal specifications. Protects against cracking, splitting, warping. Mildew-resistant coating film keeps wood free of mildew stain.