ENAMELING: PROBLEMS AND SOLUTIONS
The extensive experience of the Technical Team of CONIEX training and advising in enameling techniques has allowed us to elaborate a decalogue of the most common problems faced by our customers… In this first post we will talk about the problems when enameling parts in order to identify which are the most common ones. causes and show you the solutions in order to offer maximum support.
Previous considerations: it is important to work at room temperature (20º to 25ºC) and with a maximum relative humidity of 50 %. To facilitate the application of the enamel and to homogenize the color, it is recommended to heat the cans between 20º and 30º and shake them with gentle oscillating movements before use.
between 20º and 30º and shake them with gentle oscillating movements before use. Vigorous shaking may cause bubbles to appear.
1. THE ENAMEL DOES NOT POLYMERIZE (DOES NOT HARDEN)
The cause probably lies in incorrect enamel-catalyst ratios. To avoid this, it is very important to use a scale and work with the right quantities following our technical sheets.
2. SOME AREAS OF THE PART ARE POLYMERIZED BUT OTHERS ARE NOT.
The enamel-catalyst mixture has not been carried out correctly. Mix accurately for at least 60 seconds, so that it is completely homogeneous, i.e. all resin molecules have bonded to the catalyst molecules. For this purpose, it is important to use a container
appropriate to the mix size. Always apply the resin first and then add the catalyst. The way of mixing is very important, because if you only mix “in circles”, as the resin is thicker than the catalyst, the catalyst remains on the surface and the resin will not polymerize correctly. Mix for 1-2 minutes, from top to bottom with sticks, preferably square or flat spatulas, as this avoids or minimizes unwanted bubbles.
Scrape the bottom and walls of the vessel to avoid uneven areas.
3. “WATERS”, DULL AREAS OR WHITISH VEILS ARE GENERATED.
There are three reasons for this:
– an excess of catalyst has been added to the mixture.
– the catalyst has hydrolyzed
– the humidity in the environment is too high
The solution is to mix accurately with scales, to have a humidifier and to ensure that the catalyst is in good condition before mixing.
4. THE ENAMEL DOES NOT RUN OR RUNS POORLY
The reason may be either that the mixture is too dense or that the piece is too cold. In these cases, it is advisable to add polymeric diluent additive or, in the case of the pieces, to heat them on the enameling table at about 60º before proceeding with the application.
5. BUBBLES IN THE ENAMEL
LARGE BUBBLES, ALWAYS IN THE SAME PLACE
The reason is that the parts are either non-uniform and have pores or that there is moisture in the pores. The solution lies in ensuring that the parts are well cast and that, if electroplating has been applied, it has been done correctly.
In addition, the parts must be very dry and free of oil. Finally, it is advisable when we have this problem to heat the pieces on an enameling table at 80º and finish the process in an enameling oven at 50º.
BUBBLES OR MICROBUBBLES ON THE ENAMEL SURFACE
The reason is that the air in the bubbles does not have time to escape during baking. It is therefore important to mix the mixture gently and to heat the pieces before applying the glaze. Before placing them in the oven, it is recommended to check the pieces and if any bubbles remain, flame them with a small blowtorch.
MICROBUBBLES IN THE ENAMEL INTERIOR
They are caused by over-stirring the mixture and allowing air to enter the mixture. Although they are only visible in transparent colors, mixing gently and keeping the pieces warm will prevent these microbubbles from appearing.
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