Enamelling: problems and solutions (I)

Enameling problems: causes and solutions

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 homogenize the color, it is recommended to heat the ESMALTEX jars between 20º and 30º and shake them with soft oscillatory movements before using them. To shake them energetically can cause the appearance of bubbles.

Most common problems:

1. Enamel does not polymerize (hardens)

The cause probably lies in the fact that the enamel-hardener ratios are incorrect. In order to avoid this, it is very important to use a scale and to work with the appropriate quantities following our technical sheets.

2. Some areas of the part are polymerized and others are not.

The hardener-enamel mixture has not been carried out correctly. Carry out the mixture precisely for at least 60 seconds, so that it is completely homogeneous, i.e. all the molecules of the resin have joined the hardener molecules. For this, it is important to use a container

suitable for the size of the mixture. Always put the resin first and then add the hardener. The way of mixing is very important, because if you only mix “in circles”, because the resin is more viscous (thicker) than the hardener, the hardener remains on the surface and the resin will not polymerize correctly. It is necessary to mix during 1-2 minutes, from top to bottom with sticks, if possible squares or flat spatulas, since this avoids or minimizes the undesired bubbles.

Scratch the bottom and walls of the container to avoid inhomogeneous areas.

3. “Waters” and matt areas or whitish veils

This can be due to three reasons:

– an excess of hardener has been added to the mixture

– that the hardener has hydrolyzed

– the humidity in the environment is too high

The solution is to carry out the mixtures with a balance, in a precise way; to have a humidifier and to assure the good state of the hardener before carrying out the mixture.

4. Enamel is not fluid or don’t spread enough

The reason can 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, heat them on the Enameling table to about 60º before proceeding with the application.

5. Bubbles in the enamel

Large bubbles, always in the same place

The reason is that the pieces are not uniform and have pores or that there is moisture in them. The solution lies in ensuring that the parts are well cast and that, if a galvanic bath has been applied, this has been done correctly.

In addition, the parts must be well dry and free of oil. Finally, it is advisable when we have this problem to heat the pieces on a Enameling table at 80º to 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 come out during baking. This is why it is important to mix gently and heat the pieces before applying the enamel. It is recommended before placing them in the oven to check the pieces and if there is any bubble flaming with a small welding torch.

Microbubbles inside the enamel

They are produced by shaking the mixture too much and getting air into it. Although they can only be seen in transparent colors, mixing gently and keeping the pieces warm will prevent these micro-bubbles from appearing. Finally, a vacuum bell can be used to remove the bubbles from the mixture.

Remember that our technical team and our Applications Laboratory are at your disposal for any query on the subject.

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