The Elastostamp elastomers are liquid two-component polyurethane rubbers capable (once the two components, base and hardening agent, have been carefully mixed together) of hardening at room temperature, forming compact flexible masses with considerable mechanical and chemical resistance. Owing to these features, these rubbers lend themselves outstandingly for manufacturing moulds for the repeated reproduction of objects, simple or complex in shape, made of the most varied materials, such as cement, plaster, wax, some types of resins, etc.
The flexibility and very low shrinkage of the moulds obtained using Elastostamp polyurethane rubbers allow the reproduction of the shape of an original model many times for an infinite variety of manufactured articles, including, for example: prefabricated cement, statues, rosettes, cornices, balustrades, fountains and decorative garden articles, sanitary fixtures , decorative pottery, giftware, technical equipment, decorative candles, gaskets, mechanical components, etc.
The hardest rubbers (hardness from 40 to 70 shore A) are used in the production of large-sized shapes or those without complicated details, while the softer ones (hardness below 40 shore A) are used to reproduce objects with undercuts and many complex details.
The models to be reproduced, dollies and caissons can be made using many materials such as metal, cement, plaster, wax, epoxy and polyester resins, plastic materials, wood, glass, ceramic, natural stone, clay, rubber, leather, etc.
Before using Elastostamp rubbers with the cold pouring procedure, the models, dollies and caissons need prior treatment with special release agents; these are made with solvent-dispersed synthetic waxes (Globalwax 200 S or Globalwax 200 L) or silicone oil emulsions applicable with brush or spray can.
These release agents can be applied directly on the model or dolly, provided that they are made of non porous materials like metal, glass, plastic materials, rubbers.
In the case of models in porous materials, like cement, plaster, clay, wood, etc, treatment is necessary with products to seal the pores, without adversely affecting precision of the details. This prevents the polyurethane rubber, which is highly liquid before hardening, from penetrating the pores and creating difficulty in the subsequent “delivery” operations.
Suitable products for this purpose are sealants based on polyvinyl alcohol (VPA separator), lac, nitrocellulose lacquer and polyurethane paint, waxy pastes, concentrated soaps, etc., applicable with brush, spray, pad etc. It is necessary to wait for the volatile component (water or solvent) of the separators to evaporate completely before applying the release agents (eg. Globalwax 200S or Globalwax 200L). These are ALWAYS to be used whether the models needs sealing of the pores or not. It is worth recalling that the release agent (Globalwax 200S or Globalwax 200 L), not only aids “delivery” of the mould from the model but also prevents the reaction (with the risk of adhesion) between Elastostamp rubbers and certain insulating paints (eg. shellac). This also applies to the use of self-releasing Elastostamp (Elastostamp HD) , as the self-releasing properties only occur once the mould has hardened.
Once the models and their containers have been prepared as described previously, the Elastostamp rubbers can be applied.


The techniques mostly used are two:
1) the open air one is the easiest, suitable for reproducing flat objects with few undercuts, though they may be rich in details (rosettes, cornices, bas-reliefs, footwear soles, prefabricated panels, etc.). With this technique the rubber is poured inside an openable caisson with sealed walls, on the bottom of which the model is fixed in various ways (eg. with plasticine, resins, mechanical devices, etc) and treated (like the sides and bottom of the caisson) with special sealing and release agents as mentioned previously. The polyurethane rubber is poured directly on the model until the caisson is filled and then left to harden. After hardening, the rubber mould can easily be removed by opening the sides of the caisson to be used directly for further reproductions.
2) The hollow space technique is more complicated and suitable for the reproduction of articles with many undercuts and a lot of detail (statues, statuettes, balustrades, decorative pottery, decorative candles, giftware and artistic products, capitals, technical equipment, etc). This technique involves the construction of a dolly (in plaster, cement, polyester resin, reinforced with fibreglass fabric) formed of two tallying and separable halves. The model to be reproduced is placed inside leaving an air space of 1 or more centimetres (depending on the complexity and dimensions of the model), into which the polyurethane rubber is poured. When hardening has occurred, the two halves are separated and the model can be removed from the mould turning it inside out like a glove for small objects with minimal thickness or, more frequently, cutting the mould vertically with a cutter. In this case too, the model needs prior treatment with special sealing and release agents. The polyurethane rubber mould will then be inserted in the dolly upside down (naturally with the two halves closed again) thus acting as a containing caisson.

Preparation and use of the mixture of component A (base) with component B (hardener):
Before combining components A and B with one another, they are mixed separately to homogenise the components that may have separated during storage.
The base and the hardener are weighed in the quantity given in the technical literature, using sufficiently accurate scales (deviation of about 1 gram) and then mixed together at low rpm (to prevent air entering the mixture) using a drill with helical rotor (of the type used for mixing paints and varnishes); for small quantities the use of a long spatula is sufficient.
Mixing must be carried out in a clean container of adequate capacity for a couple of minutes. The mixture is then transferred to another container and re-homogenised for a few seconds. This ensures that any of the product that has not blended well with the catalyst remains on the sides and bottom of the first container.
The base-hardener mixture is slowly poured onto the model up to the edge, whilst endeavouring to avoid trapping any air (on this subject, air removal under vacuum for a few minutes at 20-30 millimetres of mercury might be very helpful, though not strictly necessary).
The working time of Elastostamp polyurethane rubbers varies depending on the types from 12 to 30 minutes at 20 °C, for masses of a few Kg. The time is reduced considerably at higher temperatures; it is well worth bearing this in mind during the various preparation stages.
Optimum hardening of Elastostamp rubbers takes place at temperatures between 18°C and 25°C. Good results are also obtained between 10° and 30°C. At temperatures below 10°C the rubber hardens only partially and it is not possible to obtain moulds with optimum mechanical properties, while with working temperatures above 30°C, the pouring time is considerably reduced obliging the operator to work very quickly.
Before “delivery” of Elastostamp rubber moulds it is necessary to wait at least 24 hours, considering a temperature of 20°C and a relative humidity of 60%; at higher temperatures the “delivery” time is reduced (eg. 15 h at 30°C).
The optimum chemical-mechanical properties are reached after about 7 days.

Once “delivered” the Elastostamp polyurethane rubber moulds are ready for the reproduction of copies of models, treating the mould before each pour with a thin layer of releasing wax (Globalwax 200s or Globalwax 200L) applied with spray can or paint spray gun.

The HD Elastostamp products possess self-releasing properties, therefore the use of release agents is not strictly necessary, though it is occasionally advisable to protect the mould surface from chemical-physical damage, thereby lengthening the life of the mould.