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|3501: Luminous Paste, Luminova|
Luminous paste 3501: ready to use, weight 3g, Strontiium-aluminate based pigment (green re-emmision)
Thinner 3505: 4ml (within delivery)
Shelf life: minimum 2 years, stored in dark place with maximum 20°C (68°F)
Main features: Despite maximum filling with pigment still fluid enough to distribute automatically uniformly. Best possible protection of pigment against humidity. The luminous pigment is non-toxix and not radioactive. For lacquer and thinner, in the present delivery form, are no safety data sheet and no health labelling required.
Consistency adjustment: After the last use and after delivery, the bottle should rest at least two days. Then the pigment has settled as visible in Fig. 2. One recognises at the bottom lacquer, saturated with pigment, and on top lacquer without pigment. The height H1 of this layer should be ca. 20% of the total fill height H, and if less, ad thinner drop by drop (e.g. with a screwdriver).
Tolerance: Visual judgement does. But above H1=25% rings of lacquer without pigment appear around lume dots. And with less than H1=10% the the stability of the cured paste suffers. Prevent that H1 vanishes completely, because this will spoil the paste.
Stirring: Before using the paste it should be stirred intensively, e.g. with a screwdriver between 1 and 2mm diameter. Then the paste is ready to use for some 5 minutes. If the work lasts longer, one should stirr a bit every 5 minutes to keep the optimum ratio between lacquer and pigment..
Fill hands: This is almost always successful already the first time. From the screwdriver used for stirring, a drop is taken with a fine oiler (or needle), preferably from the bottom side of the screw driver. Then the drop is sweeped over the back side of the hand, on wedge shaped apertures beginning at the wide end.. If the drop was too small to fill the whole aperture, a new is taken to continue. Don't mind how to apply the paste - it distributes uniformly almost instantly. Tthe video demonstrates how easy it is:
Set luminous dots: This is a bit tricky, and you should execise on a smooth surface. Again a drop is taken as described above, but now a very tiny, which should sit at the end of the oiler. Then the spot where the dot should be applied is only shortly touched with the drop. The size of the dot is determined by the duration of this contact. You'll get a feeling how long to touch for a desired size, but the first time, it is more reliable to bring the dot step by step to the right size with several very short touches. Again a video shows how easy it is:
Don't be afraid: The videos were made under worst conditions:
1) Applications were done right at the unlucky number "13" on the cm rule.
2) Between camera and object was just 5cm (2 inch) working height, and of course the camera shouldn't be touched.
3) The work could only be watched on the camera display.
Nevertheless no troubles. The hand got a uniform luminous inlay, because the paste distributes uniformly automatically. The dot became round instantly after first touching the cm rule, because the surface tension forces it to do so, and after the second touch it became bigger as expected. So if all the handicaps where missing, all should already go fine the very first time.
Corrections: For hands it is easy: Wash the hand in any solvent and repeat the job. For luminous dots it is difficult: Too small dots can be enlarged, but too large can't be shrinked. With some luck the paste doesn't affect the dial; and can be removed with Rodico or thinner. But the better approach is to work so carfully that lume must never be removed. 2g paste is enough for quite many hands and dots; no concern that you'll run dry because you did too much exercising.
What is known?
1) Ready to use paste based on zinc-sulphide
It can be thinned with water, but repeated drying and thinning will spoil it soon. Brightness and duration of the re-emmision are low, and this is only accepted because it matches old lume well if the lume is only partially replaced, and because with day light it is so pale that the greenish color is almost unnoticable. The paste dries fast, and on tiny drops for luminous dots the surface dries already between taking and setting them. So it requires exercise to work fast.
2) Sets with strontium-aluminate pigment, binder and thinner
As the pigment is degradede by water, only water-free ingredients are usable. Mixing small amounts for every application is troublesome, but in return the ingredients remain fresh. Brightness and duration of the re-emmision are much higher compared with ZnS. But at day light the paste appears darker than ZnS, and the yellow-greenish color is distracting for some. As the paste dries up slowly, less exercise is necessary.
Nothing makes happy
I tested quite some products, and wondered why nothing is avalable which combines the advantages of all. So I started mid 2012 experiments with lacquers, which can be opitimized by additives. Of course I wanted the choice between both kinds of pigments, but for the lacquer one formua should do.
The final lacquer keeps the paste fluid although filled near saturation with pigment. Its matte surface hides the grained structure from the pigment, and brightens up the day-color of strontium-aluminate pigment enough to look like ZnS pigment. It is used as one-component lacquer, but by adding a hardener also as two-components lacquer. So the paste can also be used for the deeply milled markers and digits on diver watch bezels, were a 1c lacquer would need months to cure. The hardener will be offered separately as soon as the investigation of dosage tolerances are finished
For ZnS pigments are cheap, and one simply takes the best available. Strontiium-aluminate pigments are available from some manufacturers. The most popular are Luminova from the inventor Nemoto, and Super-Luminova, its licensed copy from RC Tritec. There are no reasonable differences, and Luminova was chosen due to best availability. The highest intensities have pigments with green and blue emission, but as the human eye has its highest sensitiviy for green-yellow, there is no real competitor for the green type. So I'll not offer other colors unless they become avalable with comparable brightness and emission duration.
Fig 3 shows hands with Luminova on the left and ZnS on the right. The exposure was done with aperture 1:2.8 and 1/160s, at overcast sky. The hands were exposed to this light for 30 minutes. Due to the matte lacquer it is hardly nvisible that Luminova is darker and greenish.
Fig. 4 shows the same, taken with the same exposure data, but with remakably shadowed light. Already the ZnS hand is now brighter than the white background, it's emitting light though, but the Luminova hand is much brighter. For Fg. 5 only the exposure time was increased four times to simulate the adaption of the eye to the darkness. So this is how the difference is actually seen.
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