Saturday, August 20, 2011

Effect of acetone vapor on thermal printer paper


I am not sure of the chemistry involved, but I have found that acetone and isopropanol vapor will darken the ink in thermal printer paper. There is also a strange reversible blanking effect, where continued vapor application will cause the dye to temporarily become colorless. Do you know the chemistry involved?

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13 comments:

  1. Emiliano DeustuaAugust 20, 2011 at 5:33 PM

    Hi Ben.

    I think it is all about temperatures.

    The acetone vapor is condensing in contact with the paper and then immediately evaporating again cooling the paper and producing the darkening effect. In contrast, isopropanol doesnt achieve that same effect because acetone cools things easier because of the lower boiling point and lower specific heat.

    When you poured the acetone, I think that what happened was that the message was erased in the semi-solubilization proccess. After that the change of color is a matter of the evaporation of acetone and therefore the sinking of temperature.

    I might be wrong about this, however. I'm just a peruvian chemistry student.

    Cheers

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  2. AnonymousAugust 22, 2011 at 8:52 AM

    Hmm, yeah but thermal paper is supposed to react that way to higher temperatures, not lower ones. I would guess that the acetone is acting as a catalyst...or maybe it's just an effect from one of the compounds dissolving in a solvent.

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  3. AnonymousAugust 22, 2011 at 1:38 PM

    No, it's something chemical- GermX (funny story)/isopropyl does the same thing, while R134 does not.

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  4. AppletonAugust 29, 2011 at 12:13 PM

    The two major chemicals in the thermal paper - the colorless dye and the "acid" doner coreactant - will either solublize in the liquid solvent and will react to develop the black form of the dye OR the acidity of the solvent vapor will react with the colorless dye precurser to develop the colored form. Images already present on the paper will temporarily dissassociated in the presence of solvent to create the colorless structure. This will turn black again once the color molecule recrystalizes.

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  5. conairhAugust 30, 2011 at 11:57 AM

    I agree with [Appleton]'s 2nd idea. The IPA or Acetone is slightly acidic, so when it comes into contact with the Lueco dye in the paper it protonates it, causing the dye to change from colourless to black. When the IPA is poured on the receipt it is simply dissolving the ink.
    BUT
    I did an experiment with various acids lying around the house and couldn't reproduce the effect. Then I tried vodka and noticed a little bit of discolouration. My guess is that you need a nonpolar solvent (or a something which can act as a nonpolar solvent) to dissolve the dye first. I'd suggest more experiments!

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  6. AnonymousSeptember 12, 2011 at 7:12 PM

    The IPA or other solvent will dissolve the Dye/acid matrix. The printer dissolves the Dye/Acid matrix allowing the two to react, darkening the paper. When cooled, the matix solidifies dark. The solvent does the same, dissolves the Dye/acid matrix allowing the two to react.

    The reversing effect is just that. The solvent seems to favor the colorless form of the dye while in solution.

    The vapor is most likely an aerosol of solvent rather than just all vapor. So there is some liquid acetone/IPA coming out of the tip the closer the tip is to the paper. Causing the Dye/Acid to slightly dissolve and shift to the colorless state, then changing back when dry.

    Rich

    BTW: Love your Blog.

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  7. nitrousMay 27, 2012 at 6:40 PM

    It would be interesting to see what happens with thermal paper that has no printing on it. Most of the thermal papers are a lactone dye with a suitable developer such as Bisphenol A in a solvent that keeps the two apart. The thermal print head "melts" the solvent, allowing the dye and developer to come into contact. THe resultant protonation of the Dye changes allows it to undergo a ring opening, the net effect being a conjugated state that is colored. An example is the molecule "crystal violet lactone", which is a closed ring system and colorless in this state (leuco state).

    One of the solvents for this process is said to be alcohols. For the color to disappear "temporarily", the vapor (acetone or isopropyl alcohol) must temporarily allow for closure of the lactone ring. This would create a deconjucated system and, at room temperature, the leuco state.

    I think that the reasonable explanation for the chromatography effect seen with liquid solvent is that the ring closure still occurs but because it is in a liquid phase, it moves to the periphery of the liquid.

    Doug

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  8. Ben KrasnowMay 28, 2012 at 1:08 PM

    nitrous, thanks for the info!

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  9. Thermal Paper DirectFebruary 18, 2014 at 12:03 AM

    This comment has been removed by a blog administrator.

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  10. Thermal Receipt PaperFebruary 23, 2016 at 10:14 PM

    Hello Ben, interesting discovery. I think maybe the acetone and isopropanol vapor have chemical reaction with the existed dye on the thermal paper. As is known, thermal paper has a black image out on heat since there are dyes coating on its surface.

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  11. actuallyaxleyFebruary 5, 2017 at 2:49 PM

    Can anyone suggest a way to reverse this reaction permanently?

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  12. RudkavJune 16, 2018 at 4:01 AM

    This comment has been removed by the author.

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  13. RudkavJune 16, 2018 at 4:03 AM

    Thanks for sharing information regarding thermal paper rolls.

    ReplyDelete

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