Metals and finishes.

How does a hinge, lockset or door closer become a particular color and texture? Hardware items are available in many different finishes intended to enhance the appearance, durability and even the cleanliness of each product. Methods of finishing architectural metals depend on the base material and the desired appearance result.

ANSI/BHMA A156.18-2006 American National Standard for Materials and Finishes establishes code numbers and finish test methods for finishes on various base materials. It includes criteria for viewing comparative finishes to the BHMA match plates and establishes five categories of finishes.

The code numbers found in this standard are commonly referred to as "three digit" finish designations as opposed to the former "US equivalent". The main advantage to using the three digit designation is that the base material is automatically described. For example, US3 describes the color and texture of a bright brass finish, but does not include any information about the base metal. On the other hand, 605 is the designation used for a bright brass finish on brass base and 632 is bright brass plated over steel.

Why is this important? Two common situations where the base material is critical are fire-rated openings and exterior openings. Fire-rated doors are required to be self-closing, self-latching and hung on ferrous hinges or pivots. The melting point of steel is much higher than that of brass or bronze allowing a steel hinge to withstand the high temperatures of a fire without causing the door to sag and possibly become unlatched.

Exterior doors, or doors in corrosive areas such as swimming pools, should avoid the use of steel hardware. There are many steel alloys, but one in particular bears notice when it comes to hinges: stainless steel. This steel is composed of some chromium, which reacts with oxygen in the air to form a very thin film of chromium oxide on the surface of the steel. This oxide becomes a protective layer, preventing the steel inside from reacting to any other elements.

The main benefit of stainless steel in hinges is that the metal won't rust, even when exposed to salt water and salt air, where a steel hinge alone would begin to rust within a year. Specifying US26D (satin chrome) finish for these examples omits the base metal description. Instead, using 652 for the fire-rated door and 626 for the exterior door describes steel and brass or bronze base metals respectively. What if the door is both fire-rated and in a corrosive environment? Stainless steel qualifies as a ferrous material and 630 (satin stainless steel) is usually acceptable as a matching finish.

BHMA provides sample finishes called match plates that are used for comparison to actual finishes and are the basis of determining the appearance of each finish description. Among the most common finishes are the textures defined as bright and satin. By definition, bright is reflective to almost a mirror-like characteristic and satin is a smooth dull finish with a directional pattern. Another popular finish definition is oxidized which is described as "converted to oxide by combining with oxygen or removing hydrogen" This is the method used to create 613 (oil rubbed bronze) finish also called US10B.

In order to compare finishes, article 3.3.2 states that "Comparative finishes shall appear the same as the BHMA match plate when viewed two feet apart and three feet away. The two samples shall be under the same lighting conditions and on the same relative plane." This allows for slight variations in finish appearance that may be more obvious if the two samples are placed directly next to each other. The other practical explanation to this logic is that two different hardware items are usually not placed exactly next to each other when applied to a door.

Test requirements for finishes include: salt spray test; perspiration test; humidity test; abrasion resistance test; and ultraviolet light and condensation test. ANSI/BHMA Standards for each product type will describe the required finish tests for that particular hardware item.

To acquire CEP points, answer the following questions:____

You will need to look in a manufacturer's catalog or ANSI/BHMA A156.18 for assistance with the questions.

1. What is the ANSI/BHMA Standard for Materials and Finishes____

2. For each of the following openings, select a finish using the three digit finish designation

a. Exterior door, satin brass____

b. Fire-rated door, satin brass____

c. Fire-rated door in a sewage treatment plant____

d. Public washroom door, bright chrome____

3. According to ANSI/BHMA A156.18, how far apart should two finish samples be placed for comparison?____