how to make the attached document big enough for customer

Question

below is my receipt code when i print using thermal printer the print out are not big for customer how can i increase the size

'receipt.Add(malignleft)

receipt.Add(malignleft + "----------------------------------------- ")

'receipt.Add("----------------------------------------- ")

receipt.Add(String.Format("{0,-17} {1,17}", "Pin: " & MdlConn.tCompany.company_pinno, "Vat: " & MdlConn.tCompany.company_vatno))

If bill Then

receipt.Add(String.Format("{0,-17} {1,17}", Now.ToString("dd-MM-yyyy hh:mm:ss"), "Bill No: " & tReceipt.receipt_ref))

Else

receipt.Add(String.Format("{0,-17} {1,17}", Now.ToString("dd-MM-yyyy hh:mm:ss"), "Rct No: " & tReceipt.receipt_ref))

End If

If bill Then

receipt.Add("========================================= ")