Lafarge Prestia solves many technical problems,
    
such as...

For all forming processes

• mold surface problems: plasters with impurities (iron oxide, hard particles) because the mold surface will not be smooth enough to shape high quality products
• black spots: high iron content in plaster will create black spots on clayware
• inconsistency: inconsistency of plaster setting time (too short : workers lack time to cast properly; too long : lower molds output/shift) brings lower productivity and inconsistent quality of molds; therefore casting performance will be inconsistent
• set plaster lumps: plaster badly protected from moisture will have lumps that will destroy surface of clayware

Specifically for the jiggering and jollying (Roller machine) processes

• mold cracks: too low strength will make the mold crack under the pressure of the machine
• warpage: wrong level of permeability will yield too soft greenware after forming, and then create warpage problem after firing
• fast setting: too fast setting time of plaster : not enough time to release bubbles, which results in lower strength, so risks of breakage during the handling of molds

Those problems put the product quality of  tableware  producers at risk and increase the production costs a lot (bigger greenware waste, bigger plaster consumption because of shorter mold life, etc…). That's where Lafarge Prestia wants to help !

Benefits with Lafarge Prestia plasters

For all forming processes

• Our plasters have no harmful impurities (iron, hard particles) because they are made with the purest gypsum, perfectly cleaned, and we have installed more than 60 magnetic separators on our production lines. We therefore believe that our plasters are the very best for Bone China and Porcelain.
   
• Perfectly consistent setting time and demolding time, through formulation know-how, specific high tech process and on-line process parameters control, high frequency quality testing and ISO 9002 warranty
   
• Our packaging is specially designed to prevent water to get in contact with plaster powder and form hard lumps in  bags

• We produce both alpha and beta plasters and our expertise in adapting the ratio alpha/beta to achieve the proper strength for jiggering and jollying processes serves the worldwide leaders in Bone China and Porcelain.
   
• We know how to control the pore size distribution in molds made for tableware and how to make absorption homogenous on every part of the mold; therefore our plasters yield the right permeability and avoid problems of too soft greenware and warpage.
   
• Lafarge Prestia offers plasters with convenient setting time; our technical support team will help customers get the best casting performance, whichever their way of mixing plaster and water (hand mixing, conventional mixer (high speed or low speed), vacuum mixer, etc…)

Lafarge Prestia Products range

Plaster range for jiggering and jollying (Roller machine)

Prestia Roller 55, Alphacast 59 and Roller 59 are formulated mixtures of alpha and beta plasters offering excellent compromise of strength and abrasion resistance. The mold surface obtained with those plasters will be smooth and strong.

Prestia Roller 55 offers the highest strength. Prestia Alphacast 59 offers the highest permeability.

Prestia Roller 59 is widely used in stoneware and porcelain products

 

We will be glad to send you data sheets upon request. Please contact us now.


Casting range

Prestia Supercast is a plaster specially designed for solid casting. It offers high strength while offering a good absorption level.

Prestia Regular SP and Prestia Cast are plasters formulated for drain-casting. Prestia Regular SP is recommended for the casting of Bone China and Porcelain. Prestia Cast is widely used in Stoneware and dolomite casting.

We will be glad to send you data sheets upon request. Please contact us now.

Prestia Case range

Please click here to go to specific website page.

We will be glad to send you data sheets upon request. Please contact us now.

Ram-pressing range

Prestia Form TH is a plaster designed for the ram-pressing process, yielding very high mechanical strength and compatible with all types of ram-pressing machines.

To know more about usage conditions and technical tips, please scroll down this page.

We will be glad to send you data sheets upon request. Please contact us now..

Our standard payment terms are Telegraphic Transfer before delivery or irrevocable Letter of Credit. We are currently preparing the possibility for customers who find it more efficient to pay through internet with credit card.

We will be glad to give you a price quotation. Please contact us now.

Meet our team on our Customer Assistance page

Any other question ? Please contact us now.

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Some technical tips

• The most important and most simple : Use correct plaster/water mixing ratio !
• Sprinkle plaster into water slowly and allow it to soak for one minute.
• Mix the plaster-water slurry 12 to 4 minutes maximum, preferably with vacuum mixing.
• Blade type (size and shape) stirring time and speed, water purity and plaster/water ratio have an influence on working time, mechanical strength and porosity of hydrated plaster.

• Bags must be kept dry in a closed room and must be stored so as to avoid direct contact with the ground, protected from moisture and condensation.
• It is recommended that product be used within 4 months of manufacturing date.
• First In First Out (FIFO) stock management is highly advisable, of course.

Notes About Mould Casting

To obtain the best from Prestia plasters, rigorous and precise mixing conditions are essential.  Any variation can modify plaster setting mechanisms and affects the porosity and mechanical strength of the moulds.

Temperature
The mixing water temperature significantly impacts on porometry and therefore absorption characteristics of the moulds.  To maintain consistent performances, we recommend working at constant temperature.

Contamination
It is preferable to use a water as clean as possible in order to limit the introduction of soluble salts which could be prejudicial to the moulds quality.  It is recommended to work with drinkable water.

Setting time and viscosity (fluidity)
As well as consistency, the Prestia range of plasters offers a wide choice of setting times and fluidities.  The control of the setting time (short or long) is essential to meet the needs and requirements of the mold shop.

Absorption
Prestia industrial plasters cover a wide absorption range, the most absorbent being able to increase the number of casts per day by delaying the saturation point of the moulds .
The control of the hemihydrates and the knowledge of formulation allow us to provide at the advised water / plaster ratio, a fine and homogeneous capillary structure with a high absorbent effect, combined with a high water storage capacity .
These performances will be optimized through a controlled drying atmosphere.

Strength
The homogeneous and compact structures of Prestia plasters allow a high mechanical strength development and will commonly give 50% superior shelf life, as compared to that of ordinary plasters.  Moreover, the use of Alpha plaster gives the possibility to increase the mixing ratio and to contribute to a better mould strength.

Mixing equipment
Mixing equipments should be in stainless-steel, in good shape and clean before use.
Use preferable a propeller with axial flow (boat propeller type) or with 4 blades at 45 to pull down the mixed plaster slurry without turbulence.
The motor power should be strong enough to provide a constant rotation speed.  
Ideally, the motor should be equipped with a speed variator in order to adjust the propeller speed to the slurry viscosity and completely mix it (no stagnant area on the surface). 

Mixing ratio
The necessary quantities of plaster and water must be carefully weighed on a regularly calibrated scale.

Mixing ratio variations can definitely affect the performances of the moulds, especially their wear resistance and absorption.

Sprinkling and soaking
This step is important, as it allows the powder to wet slowly and releases entrapped air.  This improves the final mixing.

Mixing
Mixing conditions must be controlled in order to avoid any variations in the mould quality.  They are adjusted (speed and duration) to obtain a good and complete circulation of the slurry.  The uniform dispersion of the plaster grains will give a homogeneous mix with no lumps.
With appropriate mixing equipment, speed should be between 300 and 500 rpm (and never exceed 800 rpm except for small mixers).

Casting
The case mould should first be soaped on all working surfaces with an appropriate demoulding agent.
To avoid any air entrapment, the mixed slurry should be cast slowly at constant speed.  The pouring lip should be close to the case mould and the slurry should be poured on one side of the case mould.

Drying
Drying is an important step in mould making.  It allows the extraction of surplus water and helps the moulds to achieve optimum porosity and mechanical strength.  The drier must combine:

- a fixed and homogenous temperature at all points,
- a rapid and uniform air circulation (space out moulds),
- a controlled humidity (permanent renewing of the air) .

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Special advice for Prestia Form TH: Purging the die

• Carry out the operation with care : not too early to prevent any breakage of the mould, and not too late to develop sufficient porosity.
• The start of purging corresponds to the plaster end-of-setting time, thus occurs when a firm pressure of a thumb does not leave any print.
• It is possible also to follow the temperature increase of plaster during the crystallization : put a thermometer into the mold center in a small cavity.
• When the temperature has reached 8 to 9 degrees Celsius above room temperature, purge at about 0.05 bars during 30 seconds.
• Increase the pressure by 0.25 bar per 15 seconds up to 1 bar.
• Stay at 1 bar during 1 minute.
• Increase the pressure by 0.5 bar per minute up to 5 bars.
• At about 3 bars, the mould should be separated from the model and held vertically.
• The pressure is held at 5 bars during 1 hour
• Use : Fix the mold on the press plates rigidly avoiding any overhang (by correcting -if necessary- any alignments defects in inserting plaster layer).

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Our logistic know-how, our flexibility in production and our location very close to Bangkok harbor (Laem Chabang) enable us to offer short delivery time to Asian countries. Examples of shipping time between Laem Chabang and…

Weight and volume in relation with the mixing ratio

A customer's story… on how Lafarge Prestia plaster helps to decrease production costs

We recently asked Mr. A., Production Manager in a Bone China tableware plant located in South-East Asia why he enjoys using plaster from Lafarge Prestia. Here is his answer :

"(…) Since I started using Lafarge Prestia plaster, I can bring down my production costs by more than 5 % and reduce the cost of purchasing plaster by 12.5%.

Why ? Because of the better mould life I get with Lafarge Prestia plaster. It is longer than the mold life given by my previous European supplier. Furthermore, I can also reduce the cost of inventory because I do not need to stock so big quantities as with the imported plaster from Europe.

Another good point about Lafarge Prestia is that they really involve themselves in my plant. They  recently sent a technical support engineer over here who stayed one week to fine tune a new plaster to fit a production line where I was using a European plaster. When he left, everything was OK, we just had to check the mold life, and it was also OK.  I like suppliers who like to get their hands dirty ! Lafarge Prestia is one of them."

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Purchasing conditions

• Standard packaging is 35kg bags, specially designed to preserve the plaster the longest and resist even tough handling, except for Prestia Case plasters (25kg bags) and Prestia Form TH (40kg bags).
• We supply the bags on strong pallets.

For export markets, we prefer to ship 21 tons per containers (except in Korea where maximum container load is 17 tons and Tokyo harbor where maximum load is 20 tons)

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Influence of the different parameters on the final performances

Technical tips

Weight and volume in relation with the mixing ratio and more tips

Purchasing conditions

Special advice for Prestia Form TH

A customer's story…on how Lafarge Prestia plaster helps to decrease production costs

Influence of the different parameters on the final performances
Thanks to their formulation, Prestia plasters are less sensitive to working conditions than ordinary plasters.  However, it is recommended to follow rigorous working procedures in order to maintain a constant level of performance. Here is a summary of the influence of the main parameters on setting time, fluidity, absorption and mechanical strength :

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The data presented in this document are in accordance with the present state of our knowledge, but do not absolve the user from carefully checking all supplies immediately on receipt. We reserve the right to alter product constants within the scope of technical progress or new developments.

The recommendations made here should be checked by preliminary trials, because of conditions during processing over which we have no control, especially where other companies' raw materials are also being used.

Prestia is a registered trademark of Lafarge Prestia

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