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Roseart crayons have a higher wax content than Crayola crayons. This can actually be seen when holding the two brands side by side. This results in faster melting of Roseart crayons.
The formulas differ further, in that Crayola crayons have more pigment than Roseart crayons. The higher pigment in Crayola crayons means the colors are more vibrant, and a darker color tone can be achieved.
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Yes, the type of crayon given out at restaurants is neither of those brands you first asked about. They are generally a much less expensive crayon, and there are many different ones. Their formulas are entirely different than either Roseart or Crayola, and it is impossible to know what each of those crayons is made from. Their formulas vary considerably from maker-to-maker.
Are you trying to find crayons that melt easily or ones that don't? We know Roseart crayons melt easier, due to their higher wax content, and Crayola crayons do not.