THE PROJECT

200

FORMULATIONS

Nearly 200 formulations were designed and tested. Out of all the compositions, only two were finally selected thanks to the correct achievement of desired properties in terms of tarnishing resistance, mechanical properties and cost

2000

LAB MANHOURS

2000 hours totally dedicated to this project from June 2014 till February 2016.

100

KGs SILVER USED

In our laboratory, more than 100 kg of fine silver were used for tests related to SILNOVA® project, before any industrial test started. After that, casting sessions were performed, for a total number of 100 flasks castings, and more than 50 kg of alloy were produced in sheet and bar form.

400

SAMPLES

Total 400 samples for evaluation of internal porosity and surface quality through cross section analysis; 1600 images captured during this investigation. More than 250 hardness measurements in the as cast state. Total 50 age hardening profiles done summing up to other 200 hardness measurements. Total 50 determinations of crystal grains in the as cast state.

40

TESTS SESSIONS

40 sessions of accelerated tarnishing test were performed; in 30 sessions the two “screening test” (TAA + Perspiration test) were performed on lab samples; in the remaining 10 sessions all the six selected reference tests were performed, including finished jewellery pieces like rings, plates, chains.

6

EXTERNAL PARTIES

3 jewelry manufacturing companies (for production of samples and industrial scale tests).

3 Legor Group branches (employees using bracelets for real-life tests).

1600

IMAGES

500

MEASUREMENTS

WHICH TESTS HAS SILNOVA® ENDURED?

No alloy in the jewelry Market has till date undergone so many different corrosion tests, and in such harsh testing conditions. Our benchmark to this concern was that of the fashion accessory industry, in which the tests we used are well known.

ACCELERATED CORROSION TESTS

Various accelerated tarnishing tests were selected and used for the evaluation of the corrosion resistance of the new alloys, with different objectives:

  • RESISTANCE TO SULPHUR COMPOUNDS

    Sulphur corrosion tests, in their many variants, are the most common way to assess silver resistance to tarnish. This because sulphur compounds are among the most common and relevant agents of aggression to silver; for long time this test was the only one performed and judgement of resistance was made on the base of its sole results.

    Thioacetamide test according to UNI EN ISO 4538:1998 standard (duration: 24 hours)
  • RESISTANCE TO SWEAT

    These methodologies assess resistance to contact with skin. The item is put in contact with a solution of artificial sweat, either directly to the liquid or to the solution vapour.

    Perspiration test according to UNI EN ISO 12870: 2009 standard (made for spectacle frames) (duration: 24 hours).
    Artificial Sweat test according to NFS 80-772:2010 standard (duration: 24 hours).
  • RESISTANCE TO ENVIRONMENTAL CONDITIONS

    Well known in the fashion industry, these tests assess long-term exposure to chemical compounds present in leather, and the effect of saline atmosphere in hot, humid environments.

    Damp Heat with leather according to UNI EN ISO 4611:2011 standard (duration: 96 hours)
    Neutral Salt Spray test according to UNI EN ISO 9227:2012 standard (duration: 96 hours)
  • RESISTANCE TO CHLORINE

    Known also as “swimming pool test”, this procedure assesses the impact of corrosive chlorine based solutions, such as can be found in bleach, detergents and pool waters. TAA test and Perspiration test are used for a fast evaluation of the corrosion resistance; this tarnishing screening was made on lab samples mounted in resin and then polished. The samples that gave us good results in these two “screening tests” were then submitted to the other four tests.

    Active Chlorine test according to an internal procedure (derived from UNI EN ISO 105-E03 for textiles industries) (duration: 24 hours).

    The six tests were performed not only on lab samples but also on a real piece of jewelry like lost wax casting ring or ring made by mechanical working operation.

    REAL LIFE TESTS

    No other real-life study in the jewelry market has been conducted with such a large amount of data and participants from different countries for such a long time, giving strength and demonstrating our claims.

    9 MONTHS OF CONSTANT TESTING

    SILNOVA® is the result of a systematic documentation process, never used before within this sector, that scientifically combines laboratory tests with real-life tests.

    • The first test involved 6 people in 3 different countries for 9 months of duration, and periodic control was done on each of the bracelets. The same kind of test was then repeated on a larger amount of users for 9 months as well, using only a single object alloy for each of the users.

    • Real life test was performed by assembling 6 bracelets composed of beads made with 6 different silver alloys and with 2 gold alloys (yellow and white color) at title 375‰. All the beads were made by lost wax casting and submitted to a standard polishing process.

    • No passivation or galvanic deposition were applied on any of the items.  All the beads were submitted to a thermal treatment from the as cast state in order to increase the hardness and to improve the scratch resistance as much as possible.

      The purpose of the test was to evaluate the corrosion resistance of the bracelet during the normal use in the real life.

    • We involved the Legor Group branches and dealers in Bangkok, Mumbai and New York.

      We chose testers with different work activities, who used to live in totally different conditions in terms of humidity and temperature. We have monitored our silver alloy reactions also during their leisure time sport activities. The aim was to gather photographic documentation which was comparable and closer to reality as much as possible, over a period of at least one year.

      An impressive R&D project, lasted more than 3 years, that has seen 186 plausible formulations subjected to thousands of laboratory tests, and to the tests of the real life.

      GOALS ACHIEVED

      • TARNISH RESISTANCE

        Both the accelerated and the real-life tests concluded that SILNOVA® formulations outperforms, in terms of overall tarnish resistance all the silver alloys it was compared with. This is made possible also by the use of palladium as an alloying element in the formulation. Most interestingly, the resistance of SILNOVA® is comparable with that of the white Ni-Pd-free 375‰ gold formulation, our positive reference for the project.

        • Based upon the large base of tests made, we can state that SILNOVA® fulfills the expectations of the research project, and the goal of obtaining the highest resistance to tarnish ever met by a silver alloy for jewellery use. Silnova resists to tarnish as much as a 375 gold alloy, and as much as 20 times as a Sterling silver. Time is not stopped on your SILNOVA® jewel, but its effect is delayed in a way never done before.
        • This definitively proves that SILNOVA® can be used natural, without plating on top.*
      • PROCESSING

        Alloy SILNOVA-01 proves suitable for the production of 925 silver jewelry using investment casting in closed systems, and for the production of semi-finished items by mechanical working such as sheet, wire and tube using static and continuous casting techniques.

        SILNOVA® guarantees freedom in manufacturing processes; in fact the adequate hardness obtained by heat-hardening treatment makes it resistant to wear.

      • HARDNESS

        Although the as-cast hardness of SILNOVA-01, set at 43 HV, is lower than the 50 HV initially set as a minimum hardness value, this alloy has a major age-hardening potential. The hardening can be obtained with a single-step hardening made at 450°cx45’, allowing the hardness to rise up to 115 HV, a value that is responding to most of the jewelry applications requests.

        The hardness obtained by SILNOVA® alloys represents the best compromise between antitarnish properties and processing needs.

      • PATENT

        SILNOVA® alloys are protected by patent at Italian and international level, thanks to their innovative formulations.

        *Remarks: SILNOVA® does not claim to be a stainless or inoxidizable alloy. It does not promise that it will never discolour; that would be a false statement. Its promise is that the discoloration will occur at a much lower rate than a regular silver, and that it will be easier to remove.

        In order to standardize their behavior independently from stock life, SILNOVA® jewels after finishing have to be passivated using T-Pro solution from Legor Group. This step will ensure that the actual lifetime of each jewel starts in the very moment in which the item is worn for the first time, not at the time of production. Full information on the correct use of T-PRO is available in the SILNOVA® technical specification documents.

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