Both skim coat and wall putty correct surface imperfections and defects. However, to put it simply, the skim coat is for more noticeable defects such as honeycombs and waviness on bare concrete. It’s also used to give walls a smoother texture if the bare concrete is rough or bumpy. Wall putty is for minor imperfections such as hairline cracks and slight unevenness on a primed or painted wall.
There is a difference in what they’re applied on too. A Skim coat is applied on bare concrete and commonly over a large surface area such as the whole of a wall to correct waviness. Wall putty is applied on a surface that already has primer or paints and is more commonly used over smaller areas such as when spot correcting minor imperfections like hairline cracks.
Knowing that, another difference between skim coat and wall putty is when in the painting process they’re used—basically, if you’re using both for a project, skim coat comes first before putty.Because skim coat is applied on bare concrete, it’s used during surface preparation (or before the painting process). Proper surface preparation helps ensure the wall is in the best condition before it’s painted.
Wall putty, on the other hand, is part of the painting system itself. When painting a new wall and a primer has already been applied, putty is the next step. It’s used to go over any final surface defects. Then, there’s spot priming and finally the wall is ready for the topcoat.
As an indispensable admixture, HPMC (Hydroxypropyl ethyl cellulose) is widely applied in Skim coats and wall putty. The main function of HPMC in skim coat and wall putty is to thicken and retain water, providing well-balanced properties including open time, slip resistance, adhesion, good impact resistance, and shear strength.
Milacell Cellulose ether HPMC grade MH-100K (45,000-55,000 mPa.s Brookfield RV, 2% wet solution, 20℃) is popular in the application of wall putty and we also offer different grades for skim coat application, etc. For manufacturers of skim coats and wall putty, we are always looking forward to more communication with you.