formaldehyde urea of about 1 9 and contains about 6 percent of urea and formaldehyde and 3 percent of system modifier in the manufacturing vehicle excluding consideration of the internal phase the capsules of oily dye solution are uniformly in a size range of about 1 to 15 microns and represent more than 40 percent by volume of the encapsulating system the oily dye solution comprises 3 3 bis 4 dimethylaminophenyl 6 dimethylaminophthalide commonly known as crystal violet lactone and 3 3 bis 1 ethyl 2 methylindol 3 yl phthalide sometimes known as indolyl red in a mixture of solvents including a benzylated ethyl benzene and a relatively high boiling hydrocarbon oil such as one having a distillation range of 400 500 degrees fahrenheit the capsule product from this example will be compared below with capsule products from the next two examples this example is identical with example 1 with the exception that the system modifier is omitted from the manufacturing vehicle the initial manufacturing vehicle composition is 10 grams of urea 1 gram of resorcinol and 300 grams of water and the materials and the procedure are otherwise unchanged it should be noted that the colorable dye material encapsulated in this series of examples reacts to yield a colored reaction product and thereby becomes increasingly soluble in the manufacturing vehicle below a ph of about 2 7 to.