Click on the link below to retrieve a document from the Texas A&M website by Doug Householder, Gary Webb, Sam Wingington and Jason Brummer.
The A&M document includes some good information about the process. You can tell from the photographs that the document was produced several years ago but none of the information has changed so it is still a good relevant document about freeze branding procedures.
The document is specific to horses and the table listing appropriate contact times is on page 4.