Phillips bluing touch up paste or gel is very popular for touching up scratches on any metal you want to apply bluing touch up.
The Phillips blue is very clever stuff, shake it and it turns to fluid and then leaves it to stand and it returns to gel form.
The Phillips bluing touch up will turn chips or scratches from silver to black. Its very easy to apply and is quick to dry. There is plenty of gel to repair several nicks and scratches.
Instructions for the Phillips Bluing Touch up
Clean and remove any grease from the area that you want to blued.
Apply the Philips blue gel with a soft cloth and rub in all directions.
Wash the area with water to remove excess gel.
Oil well with proper oil.
Wash hands thoroughly after use.
The Phillips blue gel contains Nitric and Selenious acids that are poisonous and corrosive. Avoid contact with eyes. Wash off affected area with water. If swallowed call a physician.