Casting plaster for frames, rosettes, sculptures and statues
SPECIAL GYPSUM FOR THE MOST DEMANDING ARTISTS
Gypsum is an absolutely natural, odorless and non-toxic mineral, which can be molded in any form. For its unique features it has always been irreplaceable in the work of artists and sculptors.
The ART ROC line offers the most complete selection of gypsum and mixtures to meet different individual requirements in terms of hardness, precision, mechanical strength and surface finishing.
Our gypsum has decades of testimonies in special applications such as ceramics, dental technology and building industry. This great experience makes Gessi Roccastrada the ideal partner for all artists who are looking for the best product for their business.
MADE IN ITALY COMMITTED TO THE ENVIRONMENT
The largest gypsum field in Italy is located in Roccastrada, Tuscany. 200 million years ago there was a tropical ocean with coral reefs, which has formed large calcium sulphate crystalline deposits.
Gessi Roccastrada is the largest Italian gypsum manufacturing unit covering an area of 500 hectares. Particular attention is paid to the management of the quarries; Once an excavation area has been exhausted, it is transformed into a wooded area under strict environmental quality criteria.
The gypsum from the quarries, properly selected, crushed and screened, is finally cooked and refined.
The water/gypsum ratio reported on the technical data sheet has been defined to provide a creamy and homogeneous mixture with excellent casting properties. Going to change this ratio means changing beyond the density of the mixture, a whole range of features such as absorption capacity, grip, ultimate hardness, mechanical strength and grip time. If a quantity of water is used higher than expected, we may have the obvious phenomenon of sedimentation with the heavier gypsum particles that precipitate towards the bottom of the mold, while the lightest ones together with the water remain on the surface. So we will get a soft and friable surface that will feel dusty while passing a hand.
On the other hand, if we use less water than the data on the technical sheet, we get a dense mix that will hardly drip.
It is therefore important to respect as closely as possible the rapport given in the respective data sheets.
Spread the gypsum evenly in the water. Depending on the cast size, this operation can last from 30 seconds to 3 minutes. If the dough is spread too fast, powder lumps can be formed that will hardly dissolve during the subsequent mixing.
Leave the mixture rest for about 1-2 minutes (depending on the casting size) to allow gypsum powder to get completely wet and to facilitate escape of any air bubbles that may be present inside. Avoid letting the mixture stand too long as grip times are shortened. After this time, mix the dough manually or mechanically.
Mixing time depends on size of the casting and mixer type.
If the product is not mixed for a sufficient time, you may get a non-homogeneous dough with lumps, on the other hand if you mix the product for too long you get a shortened setting time and the dough will be difficult to drip.
During mechanical mixing process, make sure that you do not absorb air inside the dough. Mixing time must never be less than 1 minute even for small quantities.
ART ROC gypsum can be packed in 25 kg paper bags or 1000 kg big bags.
The product should be used at temperatures between 5 and 35° C. Use within 6 months of production date. Protect from humidity. Do not store in direct contact with soil and protect from dripping. For more information, refer to the product data sheet or contact Gessi Roccastrada Technical Service.