technical information

Winstone Wallboards supplies the gypsum product range solely through their merchant distributor network from Winstone Wallboards manufacturing plants located in Auckland and Christchurch.

Application Guidelines

Gypsum's speed of action is increased by using a finely ground gypsum product, eg using Claybreaker™ or Soil Life®, versus applying bulk screened gypsum. But finely ground gypsum is dusty and not as easy to manage through a mechanical spreader and requires calm spreading conditions.

Gypsum mixes well with other dry fertilisers – particularly granulated fertilisers. Gypsum is also useful as a carrier to assist in the uniform application of small quantities of zinc, manganese, boron and other trace elements. Conveniently, 1Kg of gypsum has a volume of approximately 1 litre (1 tonne has a volume of 1m3). Gypsum is easy and safe to apply using conventional dry-spreading equipment.

Not all soils respond to gypsum. Those that respond best have high clay contents (30% or more), high sodium contents (exchangeable sodium > 5%) and low organic matter. As a rule volcanic soils respond to gypsum more quickly than alluvial soils and soils from sedimentary parent material.

Where to buy Gypsum

View all distributors here.

Claybreaker™

Claybreaker™ is finely ground gypsum for use on clay soils and home gardens. Pack sizes include 8kg and 25Kg bags.
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Soil Life®

Soil Life®. Finely ground gypsum for use in horticultural and agricultural situations. Pack sizes include 25 Kg bags and 1000 Kg sling bags.
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Gypsum Natural

Gypsum can improve soil structural issues such as soil compaction, contoured land, soil salinity, acid sub soils as well as reducing nutrient loss to nearby waterways. It helps reduce wind and water erosion on cultivated land. 

Screened gypsum for use in horticultural and agricultural situations. Available in 25Kg bags, 1000Kg slingbags, bulk truck and trailer deliveries. 
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Technical Information

Auckland Plant Bio Gro Certification

Christchurch Plant Bio Gro Certification

Gypsum Material Safety Data Sheet.

Gypsum is known to chemists as calcium sulphate di-hydrate ( CaSO4-2H20). Winstone Gypsum™ is a fine, off-white crystalline powder. Gypsum has a neutral pH.

The bulk density of Winstone’s horticultural gypsum is 908 kg/m3 (loose) and 1172 kg/m3 (compacted).

Winstone Gypsum™ is of very high purity (93 to 98% calcium sulphate). The table below shows the mineral analysis of major and minor components of Winstone’s horticultural gypsum.NB: Quantities are stated in ppm unless otherwise specified – indicates data unavailable.

Minerals in ppm unless otherwise specified