Proper procedures for cleaning architectural glass products

TD – Architectural Glass Cleaning Procedures

Proper Procedures for Cleaning Architectural Glass Products

Prior to beginning a cleaning project, it is strongly recommended that window cleaners test clean a small area of one window, then stop and examine the surface carefully for any damage to the glass and/or any exposed coating. The ability to detect certain surface damage, such as light scratches, may vary greatly with the lighting conditions. Daylight conditions are needed to properly evaluate a glass surface for damage. Scratches that are not easily seen with a dark or gray sky may be very noticeable when the sun is at a certain angle in the sky or when the sun is low in the sky. In addition, because different backgrounds may yield different observations, cleaning methods should be tested on all glass constructions on the building, including both vision and spandrel units.

Cleaning should begin by soaking the glass surfaces with clean water and a mild, non-abrasive glass cleaning solution. Apply generous amounts of solution to the glass surfaces with a brush, strip washer or other non-abrasive applicator, and lightly agitate to loosen the soil and debris. Immediately following the application of the cleaning solution, a window-cleaning squeegee should be used to remove all of the cleaning solution from the glass surface. During routine cleaning care should be taken to avoid metal contact with the glass surface; razor blades and metal scrapers should not be part of routine cleaning. The use of sufficient water will help prevent abrasive particles from being trapped between the glass and the cleaning tools being used. However, the window cleaner needs to be diligent in keeping all abrasive particles from scratching the glass.

Glass Association of North America (GANA) and The International Window Cleaning Association (IWCA) recognizes an additional glass cleaning technique being utilized by some professional window cleaning contractors. This technique employs the use of pure water delivered to the glass surface using a specialized extension pole. Gentle agitation with a non- scratching (non-abrasive) brush is followed by the final pure water rinse. Rinse water is generally allowed to evaporate from freshly cleaned surfaces. Therefore, the pure water used in both the wash and rinse must have a total dissolved solids content (TDS) of 20 parts per million (PPM) or less to prevent spotting and streaking of cleansed surfaces. The use of tap water is not acceptable. Effective water treatment, via ion exchange and/or reverse osmosis equipment, should be used in conjunction with delivery & rinse methods at all times. Water quality can be monitored with a hand held TDS or conductivity meter. A reading of 40 micro-Siemens/cm (0.025 Me ohm – cm) represents a TDS level of 20 PPM.

Non-Routine Post-Construction Cleaning & Restoration

Careful communication between the responsible parties should precede the use of aggressive cleaning techniques, as any non-routine cleaning carries a risk of irreparable damage to glass products.

During all stages of construction, the glass must be properly protected from construction debris such as cement, paint, varnish, adhesives and other construction material commonly found on job sites. (See the GANA/IWCA Bulletin TD 03-1003; Construction Site Protection and Maintenance of Architectural Glass). Extended construction schedules may create the need for multiple cleanings to avoid the accumulation of significant amounts of soil and debris, and to avoid potential damage. In addition to ordinary techniques for protection from construction debris used by various trades, temporary protective window films may be applied to glass. Follow specific manufacturer instructions regarding film application and removal. If the film is removed prior to job completion, additional cleanings may still be needed to prevent glass damage. Failure to remove temporary protective films by the manufacturer’s recommended date may result in aggressive methods being required to remove the film.

Glass that is improperly stored or left unprotected during construction may result in glass that cannot be successfully cleaned using routine cleaning procedures. In such situations, more aggressive cleaning and restoration techniques may become necessary, such as the use of razor blades, chemical cleaning and/or mechanical polishing. Glass surface conditions that may require more aggressive cleaning techniques would include, but not be limited to, the accumulation of paint, stain or varnish overspray; mortar, concrete or cement splashing on glass; silicone sealants and/or lubricants being smeared or sprayed onto glass and frames; and sealer overspray or run-off from adjacent masonry or stone waterproofing operations. In the process of removing tenacious contaminates from unprotected glass, particles may be trapped between the razor blade and the glass, resulting in fine scratches.

While MILLET neither condone nor recommend scraping of glass surfaces with blades or scrapers for routine cleaning, it is recognized that window cleaners may choose more aggressive techniques, including the use of razor blades, in non-routine cleaning. In such cases, use of razor blades should be limited to the affected areas of the glass. Scraping should be done in one direction only with a new blade. Never scrape in a back and forth motion as this could trap particles under the blade that may cause scratches. These scratches may be visible at all times, but in some cases they may be visible only under certain lighting conditions. Significant care should be taken to ensure the glass is not scratched. Razor blades should never be used on coated glass surfaces. Contact a professional window cleaner proficient in construction window cleaning, such as a member of the IWCA for the most appropriate solution.


When cleaning the glass in architectural windows and doors, it is necessary to determine what type of glass is being cleaned and what, if any, type of coatings may be present on the exposed surfaces. Heat- treated glass is used in most architectural glass products today for a variety of strength and safety reasons, but it must be understood that heat-treated surfaces require greater care when cleaning as GANA Glass Informational mentioned in its Bulletin TD 02-0402 Heat-Treated Glass Surfaces are Different before initiating the window cleaning process, as glass may be heat-treated, i.e., heat-strengthened or fully tempered. discussed in detail in the above referenced bulletin.

All Millet Architectural Glass products contain a Millet´s logo that indicate if the glass is tempered, heat- strengthened or laminated, but it will not indicate the glass type or if exposed coatings are present. This logo not be visible or present on all heat-treated glass products, so the lack of a logo does not mean the glass is not heat-treated.

High performance windows may be produced with a coating on one or both exposed surfaces. Low-E coatings are typically neutral in color and very difficult to see. Reflective coatings increase the reflectivity of the glass and are normally obvious. Specific glass cleaning procedures must be adhered to when attempting to clean coated or reflective glass surfaces, Consult or contact to Millet’s technical service customer & Sales representative for specific procedures of any special o specific low-e coated glass.

The plastic interlayer in laminated glass is generally exposed around the periphery of the window glass; cleaning fluids and their vapors must be kept away from this area. For cleaning laminated glass, or windows and doors containing laminated glass, do not use anything that is corrosive such as solvents, acids, bases or other chemicals. Examples of some materials that may cause harm include, but are not limited to:

1. Bleach (or other solutions containing sodium hypochlorite)

2. Acids, especially muriatic/hydrochloric and hydrofluoric (often found in glass cleaning and restoration products)

3. Acetic acid, Vinegar

4. Ammonia

5. Toluene Xylene

6. Methyl Ethyl Ketone (a.k.a. MEK) Acetone

7. Ethyl Acetate Mineral Spirits Turpentine Methanol

8. Products with labeling that states they are flammable or corrosive

Contact to Millet’s technical service customer & Sales representative for additional recommendations and cautions.

Insulating glass, laminated glass and decorative glass is glazed in many ways, utilizing glazing sealants, gaskets, and/or tapes. Glazing materials do not provide a sufficient barrier to prevent cleaning agents from entering the glazing pocket and damaging the edge of the glass product or affecting the insulating glass unit seal. The presence of weep holes is recommended but is also not sufficient to overcome the risk of improper cleaning materials coming in contact with the edge of glass products. Exposure to certain chemicals may affect the sealants of insulating glass units and the surface of decorative products. Insulating glass unit longevity may be negatively affected by exposure to certain chemicals. Contact to Millet’s technical service customer & Sales representative for additional recommendations and cautions.

The glass industry takes extreme care to avoid glass scratches by protecting glass surfaces during manufacturing and fabrication, as well as during all shipping and handling required to deliver the glass to the end user. A large percentage of damaged glass results from non-glass trades working near glass. They may inadvertently lean tools against the glass, splash materials onto the glass and/or clean the glass incorrectly, any of which can permanently damage glass.

To ensure long-term performance of the glass in a building, GANA and IWCA encourage glazing contractors, general contractors, building management and owners to be diligent in preserving the integrity of glass products. It is important to be aware of conditions that can lead to glass damage, to follow the handling and cleaning guidelines provided by GANA/IWCA and the glass fabricator, and to adhere to a regular schedule of maintenance cleaning. Generally, twice per year cleaning is sufficient; however, specific regions may require more frequent cleaning due to environmental factors and atmospheric pollutants. Contact a professional window cleaner, such as members of the IWCA, to discuss recommended frequencies for your particular building.

Quick-Reference Guide to Cleaning Architectural Glass Products

The following are things to DO:

- DO clean glass when dirt and residue appear

- DO protect glass during all stages of construction

- DO determine if coated glass surfaces are exposed

- DO exercise special care when cleaning coated glass surfaces

- DO avoid cleaning tinted and coated glass surfaces in direct sunlight

- DO start cleaning at the top of the building and continue to lower levels

- DO soak the glass surface with a clean water and soap solution to loosen dirt and debris

- DO use a mild, non-abrasive commercial window cleaning solution

- DO use a window-cleaning squeegee to remove all of the cleaning solution

- DO clean one representative window and check to see if procedures have caused any damage

- DO read the following GANA Glass Informational Bulletins (GIBs) before cleaning any heat- strengthened or tempered glass products:

         • GANA ID 01-1107 Describing Architectural Glass Constructions

         • GANA TD 02-0402 Heat-Treated Glass Surfaces Are Different.

         • GANA 01-0300 Proper Procedures for Cleaning Architectural Glass Products

         • GANA TD 03-1003 Construction Site Protection and Maintenance of Architectural Glass (in collaboration with IWCA)

- DO NOT allow dirt and residue to remain on glass for an extended period of time

- DO NOT begin cleaning glass without knowing if a coated surface is exposed

- DO NOT clean tinted or coated glass in direct sunlight

- DO NOT allow water or cleaning residue to remain on the glass or adjacent materials

- DO NOT begin cleaning without rinsing excessive dirt and debris

- DO NOT use abrasive cleaning solutions or materials for maintenance cleaning

- DO NOT ever use razor blades on coated glass surfaces

- DO NOT allow metal parts of cleaning equipment to contact the glass

- DO NOT trap abrasive particles between the cleaning materials and the glass surface

- DO NOT allow other trades to lean tools or materials against the glass surface

- DO NOT allow splashed materials to dry on the glass surface

Consult either the GANA website ( or the IWCA website ( for additional information and links providing additional technical resources.

The Glass Association of North America (GANA) has produced this Glass Information Bulletin in cooperation with the International Window Cleaning Association (IWCA) solely to provide general information as to basic proper procedures for cleaning architectural glass products. The Bulletin does not purport to state that any one particular type of glass cleaning process or procedure should be used in all applications, or even in any specific application. The user of this Bulletin has the responsibility to ensure the cleaning instructions from the glass supplier are followed. GANA disclaims any responsibility for any specific results relating to the use of this Bulletin, for any errors or omissions contained in the Bulletin, and for any liability for loss or damage of any kind arising out of the use of this Bulletin.

This bulletin was developed by the GANA Tempering Division and IWCA Glass Committee and approved by the Tempering Division and GANA Board of Directors.

History Table

02020-08-16Original Publication

Millet Glass Industry Logo is a registred trademark of Millet Glass Industry, Inc.

KEYWORDS: Cleaning procedures, Glass products,

REFERENCES: GANA TD-01-0300, Proper procedures for cleaning Architectural Glass Porducts:

This document is intended to inform and assist the reader in the application, use, and maintenance of Millet Glass Industry products. Actual performance and results can vary depending on the circumstances. Millet Glass Industry makes no warranty or guarantee as to the results to be obtained from the use of all or ani portion of the information provided herein, and hereby disclaims any liability for personal injury, property damage, production insuddiciency, or any other damages of any kind or nature arising from the reader´s use of the information contained herein.

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