Are these evil thermometers puzzles free to print?

Yes. Generate the puzzle above and print it with its answer, at no cost and with no sign-up.

Does every puzzle have one solution?

Yes. Most tilings are not pinned by their own counts at all, so the generator keeps only the ones a solver proves fill exactly one way. The answer is on the second page.

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Evil thermometers

An evil thermometers puzzle is a fourteen by fourteen board of about twenty-eight thermometers, the longest sixteen squares. About one board in six at this grade cannot be finished by straight deduction alone, which is the only grade here where that is common.

Difficulty

A bigger board is harder. Longer thermometers sound easier and are what make a big board solvable at all: each one has only as many states as it has cells, so a grid of short ones leaves the counts with too little to pin down.

14×14 board, 26 thermometers. Mercury fills each thermometer from its bulb and never skips, and the numbers beside each row and column count the filled squares in that line.

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Thermometers Evil

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Thermometers Evil · Solution

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How to solve a thermometers puzzle

The grid is tiled with thermometers, each a straight run of squares with a round bulb at one end. Fill each one from its bulb, never skipping a square, so that the numbers beside each row and column count the filled squares in that line.

The method

1Start with the lines that have no choice. A row or column numbered 0 is entirely empty, and one numbered the full width of the board is entirely filled. Both decide every square in the line at once, and both usually decide parts of several thermometers that run across it.
2Work each thermometer from both ends. A square you know is empty makes every square further from the bulb empty too, and a square you know is filled makes every square back down to the bulb filled. One deduction anywhere on a thermometer travels the whole length of it.
3Count what a line still needs, not what it has. Subtract the squares you have already filled from the line number. What is left has to come from the thermometers still undecided in that line, and often only one way of splitting it fits.
4Use the most a thermometer could give. If a line needs four and the thermometers crossing it could supply at most four between them, every one of them is filled as far as that line. The same argument upside down empties them when a line has nothing left to give.

The one rule people get wrong: Mercury rises from the BULB, not from the top of the page. A thermometer drawn pointing left fills from its right-hand end, and the bulb is the only thing on the board that says which end that is, which is why it is drawn so much wider than the tube.
What the answer page shows: The same board with the mercury drawn in, so each thermometer shows at a glance how far up it was filled.
How the grades differ: A bigger board, tiled with longer thermometers. The longer ones sound easier and are what make a big board work at all: a thermometer has only as many states as it has squares, so a large grid of short ones leaves the numbers with far too little to pin down.
Is it the same as a nonogram?: No. Both count filled squares along the rows and columns, but a nonogram tells you the runs in a line and leaves you to place them, while here the runs are printed on the board and the only question is how far along each one the mercury reaches.
Good for: Anyone who likes a puzzle that is mostly careful arithmetic.

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Questions

Are these evil thermometers puzzles free to print?: Yes. Generate the puzzle above and print it with its answer, at no cost and with no sign-up.
Does every puzzle have one solution?: Yes. Most tilings are not pinned by their own counts at all, so the generator keeps only the ones a solver proves fill exactly one way. The answer is on the second page.
Can I make a thermometers book to sell on KDP?: Yes. The free tool makes one puzzle. The KDP thermometers maker generates hundreds of graded puzzles at any KDP trim, as a print-ready 300 DPI interior and solutions PDF.