The alkalinity of certain surface materials can bring on color loss and overall deterioration of paint on fresh masonry, concrete or stucco.

Surfaces and materials with high alkalinity can damage your paint.

1. The alkalinity of new mortar, cement mixes and concrete is determined by its pH level. The pH of fresh materials is 13 to 14. It takes about 30 days for those materials to drop to an approximate pH of 9 (a lower level of alkalinity). Applying your coating to a surface with a lower alkalinity increases the chance of avoiding alkali discolorations.
2. Stucco and mortar joints contain hydrated or "hot" lime, a dry compound added to improve the workability of the material. Depending on its end use, different mortars are compounded with different amounts of "hot" lime. If more "hot" lime is added at the jobsite, it can make the problem even worse.
3. Once these surfaces are cured, the introduction of moisture into the walls can reactivate the high pH alkalinity, resulting in efflorescence, blistering and peeling of the paint film.
4. The alkalinity of "hot" surfaces will destroy an alkyd or oil product within 6 months. A vinyl acrylic coating will perform slightly better; however, it too will ultimately fail. An acrylic coating will give the best service performance.
   

Remove all surface contamination (peeling paint, heavy chalk, efflorescence, laitance, concrete dust, etc.) by hand- or power-tool cleaning or washing with an appropriate cleaner. Rinse thoroughly. Allow to dry.

Cracks, voids and other holes (which allow moisture into the surface) should be repaired with an elastomeric patch or sealant, or appropriate caulk. Rough surfaces can be filled using Loxon^® Block Surfacer, for a smoother surface.

All new surfaces must be cured according to the supplier's recommendations – usually about 30 days (i.e. let it sit). Remove all form release and curing agents.

If painting cannot wait 30 days, allow the surface to cure 7 days and to a pH of less than 13. Prime the surface with Loxon^® Acrylic Masonry Primer.

During the preparation phase, look to a sealer like Loxon^® Block Surfacer to smooth out those rough surfaces. After the surface has cured, use a primer designed for porous surfaces, like Loxon^® Concrete & Masonry Primer/Sealer. For a long-lasting coat that resists water streaking, finish up the job with Emerald Interior Acrylic Latex Paint. Or you might consider a durable, fast-drying paint, like Loxon^® XP Masonry Coating.