Do’s and Don’ts of Cleaning Historic Windows
Minneapolis is home to some stunning historic properties, from the commercial buildings in the Warehouse District, to the 20th Century homes Uptown. Many buildings built before 1950 still have their original windows, and when it comes to cleaning historic windows, the process is much different than cleaning modern glass.
For starters, historic windows tend to have small, hand-blown panes, which was common prior to the 1950s, and the glass tends to have imperfections and unique designs. Most are fragile too. As such, the same modern cleaning chemicals and tools just don’t fit the job.
Do you have historic windows on your property? If so, you can’t just pick up a squeegee and start cleaning. There are some special steps you should take to preserve historic glass and historic window frames. We’ve highlighted a few tips that can help you clean your historic windows properly.
The hand-blowing process made it difficult to produce large, continuous sheets of glass. As such, many historic windows that you see in Minneapolis feature small panes built. Warehouse windows, for example, are a type of historic window style that features small panes with metal frames.
Historic windows have some special cleaning needs. If you’re approaching a historic cleaning project on your property, there are a few things you should do and not do:
- Do use lent-free terry cloth wipers. Most window cleaning companies use squeegees and sometimes water-fed squeegees to clean modern windows. That’s a problem with historic glass. The reason is that many historic windows have smaller, individual panes, rather than large expansive glass. As such, large squeegees just don’t fit.
- Don’t use abrasive cleaning pads. When selecting cleaning pads, choose a soft, non-abrasive terry cloth cleaner. Abrasive pads can leave etching in fragile historic glass.
- Do be gentle with the windows. Historic windows tend to be very brittle. The glass isn’t as sturdy or structurally sound as the glass that is used in windows today. Therefore, it’s important to be gentle when cleaning each pane. Don’t apply too much pressure, and avoid direct water contact.
- Don’t use acidic cleaning solutions. The key with a cleaning solution is to dilute it. Today’s cleaning chemicals are just too abrasive, and they can cause corrosion and discoloration on historic metal window frames. Instead, use an ammonia-free solution and warm water to remove dirt.
- Do seek professional advice. Some windows are best left to professional cleaners. Window cleaning companies can help assist in removing tough stains and dirt, and they have expertise in handling brittle, historic glass.
- Don’t confuse air bubbles with dirt. The glass in old windows tends to have a lot of imperfections, including waves, fisheyes and bubbles. Often, these imperfections get mistaken for dirt. Be on the lookout for bubbles in particular. You don’t want to spend hours scrubbing at air bubbles.
What Tools and Cleaning Solutions Should You Use?
The modern cleaning supplies you use for your windows often won’t suffice for a historic cleaning project. In fact, you might have to start with an all new set of gear.
A few recommendations:
- Terry cloth pads
- Buckets for water
- Ammonia-free cleaning solutions (Diluted dish soap or vinegar/water solutions work great)
- Razor blades for removing tough dirt and grime
- Fine pumice or fine steel wool for removing tough dirt
The key is using gentle cleaning solutions and tools. You never want to scratch the surface of the window while cleaning, or move dirt/grit that’s already on the window back and forth. Use a gentle motion one direction motion to remove dirt safely.
Stained Glass: Cleaning Tips for Property Owners
Stain glass windows are gorgeous, and often times, they don’t require cleaning. But there are a few instances when they do. For example, over time, rain runoff can leave deposits on the exterior surface of the glass – like rust from iron frames, or limescale from mortar.
These deposits can cause damage, if left to sit, and may also make the windows look scummy or foggy. Special care must be taken to protect the character of the glass.
A few tips:
- Seek professional advice – Contact a professional window cleaner or a local historic preservation society for advice prior to cleaning.
- Use the right supplies – You should avoid any tool or product that’s abrasive when cleaning these windows, e.g. steel wool or acidic glass cleaners.
- Be careful about access – Stained glass windows are typically located high up on churches, and therefore, require ladders and even scaffolding to reach. Be sure you have safe access, prior to cleaning.
In most cases, especially with stained glass, it’s best to contact an experienced conservator or cleaning company for advice.
Historic Window Cleaning in Minneapolis
Do you need help with a historic window cleaning project in Minneapolis? Clean and Clear can help.
We serve all of the Minneapolis-St. Paul region and have experience cleaning historic properties. We’re happy to provide advice, offer tips, or come out and help with a cleaning project. Call us at (612) 254-8777 for a Free Estimate or to learn more about our historic property cleaning services.