HP 900 Natural lime smooth plaster

Hessler Kalk-Glätte

HP 900 is used for smooth finishing in interior areas.

Composition of HP 900

Kalk-Glätte consists of natural hydraulic lime, white hydrated lime, marble powders and a small addition of cellulose. HP 900 contains no synthetic binders, is highly vapour-permeable (water vapour diffusion resistance factor µ ≤ 7), and its pH value of 11–13 (9–11 in the long term) creates conditions unfavourable for mould growth. 

Preparing the substrate

The ideal substrate is a lime plaster (e.g. HP9 or HP9L) or a lime-cement plaster HP 1. As a first levelling coat, use lime finishing plaster HP 90. DIN 18350 and 18550 must be observed when assessing and preparing the substrate. The substrate must be sufficiently absorbent, dry, firm and keyed, and free from dust and release agents. Highly absorbent substrates must be pre-wetted, as must substrates in very warm weather. Protect the fresh skim coat from drying out too quickly. The air and/or surface temperature must be above 5° C. Substrates unsuitable for pure lime plasters (e.g. concrete etc.) must be prepared with lime bonding plaster HP 14. On plasterboard/gypsum board substrates, after priming with Hessler Iso-Grund, a mesh-reinforced skim coat with lime bonding plaster HP 14 is recommended.

Applying lime finishing plaster

Mix the contents of the bucket with clean water. The water requirement is approx. 6.5 l for 12.5 kg (1 bucket). Apply HP 900 with the stainless steel trowel. Apply a second layer wet-on-wet and smooth it. Protect the fresh skim coat from drying out too quickly. Material requirement: approx. 1 kg/m², depending on the nature of the substrate.