Yes, it is wise to impregnate the fabric again after cleaning.
Why impregnate after cleaning?
Every cleaning agent affects the original impregnation. That is why we always recommend impregnating the canvas after cleaning to make it waterproof again and to give it extra protection against mold, dirty water and bird droppings, for example.
Sprayhood & Tent Protector is a very strong impregnation agent. We have developed it especially for use in our sail and tent laundry. We use it to impregnate and waterproof tents, boat covers, awnings, catering parasols and awnings. And with great success.
Do you have a folding trailer tent or other tent made of cotton tent canvas? Use Ultramar Canvas & Cotton Protector to make your cotton tent waterproof.