Prompt natural cement

Prompt is a natural cement, mined and manufactured in Grenoble in France. It is burned at similar temperature to lime and contains nothing more than what is dug from the earth. Natural cement has been produced using the same method for over 150 years and works well with heavy aggregates, bio-sourced aggregates and when blended with limes. Prompt has been in use continuously since the 1850's. It is a very simple material with some complex characteristics, manufactured from Argillaceous Limestone (Limestone containing some clays). It is simply mined, fired (at much lower temperatures than ordinary cement) and milled. Nothing is added to it, nothing is taken away.

Having been in use for over a hundred and fifty years it has been tested and proven well beyond the abilities of Ordinary Portland Cement.

Advantages Of Using Natural Cement:

  • Extremely fast set, which is controllable with TEMPO
  • Waterproof and sets under water
  • Good resistance to contact with the sea water
  • Low shrinkage
  • Fully controllable setting time, from 90 seconds to 30 minutes
  • Beige colour develops on exposure to sunlight
  • Completely natural
  • Good resistance to aggressive environments
  • No additions whatsoever


Prompt is a very fast setting material, however its set can be adjusted using TEMPO. TEMPO is specially designed to adjust the setting time of Prompt Natural Cement to the working pace of the professional. The set of Prompt is also affected by the ambient temperature; the warmer it is the faster the mortar will set.

TEMPO is easy to use, comes in an 80g bottle - a full bottle is a suitable quantity for a full bag of Prompt.

Setting time = Speed

Temperature of the mortar10°C20°C30°C
Setting time without TEMPO4 Mins2 Mins1 Min
Setting time with the TEMPO Dose30 Mins15 Mins10 Mins
Photo: Prompt natural cementPhoto: Tempo

Hot Lime Mortar Ltd :: Edenholme, Great Musgrave, Kirkby Stephen, Cumbria, CA17 4DP

Tel: 07717 400233 :: Email: