In 2023 stellt sich die Frage: Wie hart sollte es sein, wenn es um die Wahl des richtigen Dubliersilikons geht? Hier gibt es eine kleine Entscheidungshilfe am Beispiel der DUOSIL-Reihe von SHERA:
The higher the Shore hardness, the more rigid and firm the silicone becomes. So far so good. But anyone who thinks "silicones with a high Shore hardness are more precise" is mistaken. Especially with duplicating moulds for plaster or investment models this is not true. Plasters and especially investment materials expand three-dimensionally. If the setting expansion is blocked by a "fixed" mould, it increasingly goes towards the base of the model. The dimensions distort. Later, e.g. when casting a model, you have the feeling that you have to bend the cast outwards over the palatal seam.
When cured, DUOSIL H duplicating silicone, Shore hardness A 17, is strong enough without warping. Stabilizing frame and flask are not necessary. At the same time, it is elastic enough to give the investment material the necessary space to expand freely. The perfect compromise! DUOSIL H is also suitable for models with thin, undercut dies, for the electroforming technique and for refractory dies.
With Shore hardness A 9, DUOSIL S is the softie among the duplicating silicones. The material is designed for very thin dies. Since it is very soft and elastic after curing, the delicate dies do not break off.
Slightly harder is DUOSIL D with Shore hardness A 22. It is suitable for plaster, investment material and for electroplating.
DUOSIL EXPRESS with Shore hardness A 22 is an alternative when things have to be done quickly. The silicone sets after only 9 minutes and can also be poured with plaster or investment material. It is essential to mix the components by hand. Due to its faster reactivity, it can already harden when mixed in a device and, in the worst case, clog it.
The hardest variant of SHERA is DUOSIL EXTRA HART Shore hardness A 32. It is particularly suitable for plastics technology. Due to the higher hardness, the confection teeth sit more firmly in the silicone. The light oil layer also acts as a light separating layer to the plastic. This already gives the plastic a nicer and smoother surface. In addition, DUOSIL EXTRA HART has a very fast setting time. Here, too, the setting time is 20 minutes.
To ensure that addition-curing duplicating silicones (1:1) cure optimally, it is worthwhile to heed this little practical tip "B before A": A more homogeneous, even cure is achieved by first weighing out component B (base) in the mixing cup and then adding component A. The catalyst reacts second. The catalyst added second reacts more actively during the subsequent thorough mixing and makes the result really perfect.
A sustainable alternative to silicone are the reversible duplicating compounds made from the natural product agar-agar. This material is obtained from dried algae and is completely biodegradable. Duplicating gels can be liquefied in the duplicating gel machine or even the microwave. SHERA duplicating gels made from agar-agar are specially optimized for pouring with certain materials: SHERAHYDROKOL for plaster, SHERAFORM for investment materials and SHERAGEL for plastics technology.
Lust auf mehr? Hier geht es zu weiteren Artikeln.