It is recommended that you start with the aerosol spray for test and evaluation purposes. The aerosol spray cans are pre-mixed and ready to use which eliminates the need to dilute the Liquid Ink - you only need to concentrate on getting the correct coating thickness and laser settings as shown on the instruction sheet enclosed with each spray can. Once you’ve tried the aerosol and gotten some experience with spraying it and determining the correct laser parameters, you can switch to a foam or airbrush application of the Liquid Ink when you begin marking larger quantities. The Liquid Ink is concentrated and needs to be diluted with denatured alcohol. Please follow the instructions shown on the enclosed instruction sheet and product label. You’ll already be familiar with the proper coating thickness and it will be easy to switch if desired. There are considerable economic advantages for switching to the Liquid Ink when marking larger quantities, since a square inch of aerosol spray costs about $0.03, while a square inch of Liquid Ink costs $0.01 or less depending on the container size.