All were done in a special ink that disappeared after the messages had been opened.

Such was the way with messages transmitted in the special ink.

The image on this one is printed in a special reactive ink.

Clyde had used the special ink required in such important communications.

The special fluorescent ink in our markers makes the board come to life when turned on.

He used his own mixture of special ink on contemporary paper.

This was because he had utilized a special ink for the actual message.

He would have had to find a source for the special ink, plus a way to print it.

They used a special ink that vanished after contact with the air.

There is a special ink that can make the buttons flash.