Monday, 9 March 2009

wax temperature

waxed lines showing gap by joinNot very scientifically controlled, nevertheless I have been measuring the temperature of wax in my Tixor Malam waxpot. Usually I have had it at its highest setting (7).

When I learned to make batik in Malaysia, the wax was in a wok over a charcoal fire and was very hot, so hot that occasionally it caught alight. At those times everyone stopped work and piled sand from the floor on to the wok to put out the flames and prevent the atap (thatch) roof from catching alight. Because I'm sure a European designed waxpot would prevent wax from getting that dangerously hot, I have believed it best to set it to have the wax as hot as possible, thus staying hot and fluid in a canting for as long as possible.

More recently I have been questioning the wisdom of this logic. Firstly, if it's hotter than necessary then it's using unnecessary energy to be heated. Secondly, over-heated beeswax gets structurally 'damaged'. For sometime I have realised that long-term cooked wax goes brown, gets brittle and loses its resist qualities. More recently I have discovered (from reading) that the brown-ness occurs over about 120 deg C, and brittleness damage comes from too rapid cooling, ie contraction. A further reason for practical research into waxpot temperature is that noxious fumes are given off at 120C. Out in the open (eg in Malaysia) where fumes can move quickly out of the shelter into the general atmosphere, the chemicals can be quickly broken up, or down, by sunlight. Not so easy in a small terraced cottage in a Cornish winter/spring.

As a preliminary trial which may guide further tests, I measured the temperature of the wax at settings 1, 2, 3 and 4, over two separate meltings. The thermometer was hand held in the wax above the 'minimum level' line (ie towards one side rather than in the middle). The thermometer was held so the full bottom metal part was under molten wax. The quantity and recipe of wax were not measured, however around half was old, cooked wax, and half new. The new comprised two handfuls of Fibrecrafts batik mix (paraffin/microcrystalline mix) and one handful of Candlemakers beeswax (yellow). The ambient room temperature was 16-17C. The temperature range measured was

1 69-72C (156-162F)
2 79-84C (174-183F)
3 96-99C (205-210F)
4 110C+ (230F)

water leaking through gap in wax joinI can only speculate the temperatures above setting 4 as the thermometer stopped just beyond 110C. So approximately, 5 - 116-120C, 6 - 126-130C, 7 - 136-140C (240.8-248F, 258.8-266F, 276.8-284F). However here it says a Tixor Malam heats only to 135C.

At setting 4 (110C) I was able to wax acceptable lines on cloth (prima cotton, very fine). However, at the same temperature, further lines crossing these weren't hot enough to 'close the gap', meaning dye would leak through the closed sections of the grid. The first picture shows the reverse of the fabric with gaps by the overlap, the second picture has water seeping from the first square into the next through the gap.

I explain this to myself as, when viewing in cross-section the first line of wax (as a circle, ie the line disected) has partially penetrated the fabric but most wax is still above, because it cooled and hardened before being able to penetrate. In contrast the circle from a hotter wax line would appear more evenly above and below the fabric. When the next wax line crosses the first, it does so at a higher angle than if crossing a line sitting lower on the fabric. The leap from cloth level to top of wax line means a gap is left without wax, and additionally, wax coming from the canting cools before it can reach, never mind penetrate, the fabric. Wax applied hot enough will reach the fabric and also partially soften and merge with the previously applied wax line.

So, I turned up the heat, to setting 5 (though later viewing showed it slightly over, say 5.2). From across the room I could see fumes emerging heat-haze style, but the room didn't cloud up (the fan was on). At this temperature (approx 120C) I was able to draw new wax lines adjacent to the previous lines, and they seem to have penetrated successfully. However I was using a wide spout canting and as I had to draw slowly to ensure wax penetration I could not always make the width of the fabric before the wax had cooled. So at 5 the temperature is sufficient perhaps for small detailed work but not ideal for longer smooth drawing of lines.

update 11 March 2009
The second lot of lines drawn at 5.2 temperature crossed each other fine, but in places were unable to cross smoothly/warmly enough the earlier 4 temperature wax. A few leaks have shown up. But it's only a colour testing cloth, so nothing drastic!

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