Super Simple Heat Activated Invisible Ink (not Lemon Juice)





Introduction: Super Simple Heat Activated Invisible Ink (not Lemon Juice)

5min $5 invisible ink utilizing the already-there heat sensitive chemical on thermal paper. I think this works much better than lemon juice because lemon requires you to half burn the paper to show up.this requires much less heat.

Step 1: Get the Stuff You Need (not Much)

you need,

1.thermal paper

2.water and a cup

3.tooth picks/q-tips (to write with)

4.candle or other heat source

NOTE: If you dont have blank thermal paper just use receips from stores and gas stations (use only the paper that is shiny on the one side with dark shiny black writing). Be sure to use the part that is blank and not the printed on part.

Step 2: Add Paper

fully soak in water

Step 3: Remove the Heat Sensitive Chem

remove as much water as possible. If you have a tea bag strainer/smusher thiny it would work well.

Step 4: Finish

keep wetting and wringing out the paper untill your ink looks like whats in the pic below. the more concentrated your ink the better it will work.



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    26 Discussions

    Does this ink remain visible? or does it disappear when it cools down again? Thanks for your input.

    i became a pro member thinking there was step after step 4 --- i have done everything and have been able to get the liquid to look milky but when i use a q tip to apply it to paper and heat the paper, nothing happens. any thoughts.

    waaaaaait........ you mean I could use old receipt paper for that? as in the modern receipt paper? the smooth-feeling paper? if so, I'm buying a roll! lol

    While we are on the topic of thermal paper. There is a chemical out there that will react with thermal paper and turn it black. It is sort of a yellow color. Any thought on what that maybe.

    5 replies

    That works but, I'm looking to use it in fingerprinting application and iodine to too hazardous.

    o. u could do corn starch and iodine, starch turns purple/black, if u didnt mind danger

    I know Alcohol turns thermal paper black sometimes. It's not very consistent though.

    correct me if i'm wrong, but what this is, is soaking thermal paper in water which gets some funky chems in the water and this will be your thermal activated ink??? or do you write on a reciept???? i'm confused...0\ _ /0...grr...

    1 reply

    Great source of thermal paper is fax machine paper for old school ones, you can still buy it at most places like staples and it's pretty cheap for a large ream...


    11 years ago

    for the ink


    11 years ago

    can u use regular paper?


    11 years ago

    yea regular paper


    11 years ago

    im not sure what the problem could be but i would guess that your thermal paper is different that mine or the theremal chemical is not concentrated enough. How much paper to water did you use?

    1 reply

    it looks exactly like yours throughout the steps. Mine may be to watery so ill try less water to more paper. Also you use this on regular paper and not the thermal paper right?

    Sorry to bother, but I am having trouble with this. I follow all of the steps. I put thermal paper in the water and wring it till it turns whitish. I then apply some to a piece of paper and wait for it to dry. I then hold a lighter to it and nothing happens except maybe a brown mark from me burning the paper. Any thoughts on what i could be doing wrong?