What is a highlighter made out of?
CLAIMS 1. A highlighter ink composition, comprising: a) an acid buffer having a pKa from about 2 to about 6; b) a highlighter colorant ; and c) a liquid vehicle. 2. The composition of claim 1, wherein said acid buffer is selected from the group consisting of succinic acid, citric acid, glutaric acid, acetic acid, beta- alanine, aspartic acid, ascorbic acid, and mixtures thereof. 3. The composition of claim 1, wherein said acid buffer has a pKa from about 4 to about 6. 4. The composition of claim 1, wherein said acid buffer comprises from about 0.5 wt% to about 10 wt% of the composition. 5. The composition of claim 4, wherein said acid buffer comprises from about 2 wt% to about 3 wt% of the composition. 6. The composition of claim 1, wherein said highlighter colorant is selected from the group consisting of Basic Yellow 40, Acid Yellow 23, Acid Red 52, Acid Blue 9, and mixtures thereof. 7. The composition of claim 1, wherein said highlighter colorant is a fluorescent colorant. 8. A meth
