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Majolica Tile Decoration Problems
Section: Clay Bodies, Subsection: General
A small tile decorating company diagnoses problems with commercial bisque tiles and seeks help to find the type of tiles available in the past.
We decorate tiles by hand using the Majolica method. We thus apply a glaze-base to bisque fired tiles, decorate them and then fire the base and decoration together. We have been having great problems with the industrial-made tiles we buy (there is no problem with hand or semi handmade tile). We normally use handmade ones but need to buy commercial ones when a client requires. The industrial-made tiles are much more expensive and they are thicker and heavier so this doubles the price of transport and firing.
1) We had been preparing tiles in the same way for twelve or more years: applying the glaze-base, cleaning them, piling them up by pairs, face to face, on top of each other, and leaving them for days, weeks or even months before decorating. Then the firm we bought from stopped producing and we had to find another one. The new tiles had a strange reaction: they came out in a rash, mainly round the edges; very small hard spots, which did not go away and when fired, damaged the work enough to make it non-saleable. We just could not understand what was happening, and suffered the consequences as hundreds had to be thrown away. By sheer accident we found the solution, making two pictures for the same client. We laid out one on the tile stand to dry off so we could start to work and the other we left piled up. After four days, when we wanted to start to paint the second one, we found it had the 'disease'. What causes it we do not know, but how to avoid it we did! Now one long wall, in our studio corridor, has narrow movable shelves, from top to bottom where all the tiles are laid out and left to dry separately without touching each other. When the glaze-base and the tiles are dry they can be stored in piles on top of each other, as before.
The first photo shows one tile from a picture of 20 where the whole surface is affected; looking closely the small white spots can be seen.
This is the corridor where we dry the tiles. The wall has movable shelves and the shelves are built up, one on top of the other, using small bars of wood; this leaves enough air to dry them.
I have been told this happens because the new processes of producing tiles makes them stronger and this means they cannot absorb water. Thus, when they are piled up face to face (base on top of base), the water cannot escape so they cannot dry. From one firm we buy tiles in four different sizes and they are all made with different methods. The worst is 6x6in (15x15cm) as it is the most commercial one; it is so strong and hard that the glaze-base can take up to 24 hours to dry.
2) When we started using the new type of tiles we found that when fired to the correct heat the glaze surface was matte, as if not completely fired. The first way we found to avoid this was to spray the finished work, before firing, with a layer of transparent glaze. The method was expensive and unhealthy. After doing this for about six months we realized the trouble was caused because the bisque tiles we brought were under fired. Now we fire them at 980º C before starting to decorate. This is only needed for industrially made tiles; every other object where we use handmade tiles, plates and jars, can be decorated without it.
3) At the same time we started having problems with the manganese - all the outlines started blistering, we had not changed the make or type of color. Of course any poor client knows when a product he buys has changed. The solution to this was to stop using manganese and we now use 1 part brown-red with 1 part dark brown.
4) The photo shows two tiles, the back of the old and the front of the new, just seeing the different colors shows the difference in quality also the contours on the back of the old ones are much easier to clean, the new ones are made with small indented lines (which doubles the work).
5) If anyone knows a factory in Europe that still makes the old fashioned industrial tiles, send us the address. Also if you can explain to me the technical change tiles have gone through so I know what I am talking about, it would be a great help.
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