How to Clean & Care for Your Sapphire Windows

Maintaining your sapphire windows is essential to preserving their optical clarity and ensuring they continue to perform at their best, whether they’re used in scientific instruments, high-pressure environments, or high-temperature applications. But before you grab just any cleaning solution, let’s break down the best materials and methods for cleaning sapphire windows to ensure long-lasting quality.

Know Your Coat: Care Instructions for Coated & Uncoated Windows

The first step in cleaning your sapphire windows is knowing whether they are coated or uncoated.

• Coated windows often feature anti-reflective (AR), thin-film coatings that reduce glare and enhance optical clarity. These coatings can be delicate, and it’s important to clean them gently, using non-abrasive materials.
• Uncoated windows tend to be much more durable than their coated counterparts. While few substances can scratch or harm uncoated windows, this doesn’t mean you should be careless with your cleaning materials. For best results, stick to gentle solvents and soft fabrics.

The Sapphire Cleaning Toolkit: Materials You Need

Before you begin the cleaning process, it’s important to have the right materials in your toolkit.

When in Doubt, Air It Out

Compressed air is the key to removing dust particles before the solvent is applied. Simply use a can of dry, compressed air to gently blow away the dust and dirt particles. Skipping this step can be disastrous, as any dust left behind can agitate or scratch the window’s surface during cleaning. In some cases, dusting may be the only step needed to clean your optics. Unless there are visible smudges, marks, or stains on the window, it’s best to clean it with air only.

Compatibility is Key: What Solvents are Safe to Use

While it may be tempting to use an off-the-shelf glass cleaner to polish your optics, we don’t recommend it, as they can leave behind streaks that both distract and hinder performance. Look for reagent-grade solvents. Isopropyl alcohol, acetone, methanol, propanol, and distilled water are common choices. Additionally, if your sapphire window has a particular coating, check for specific care instructions to ensure the cleaning agent used is compatible.

Avoid Streaks & Scratches with Lens Tissues

When you’re cleaning sapphire windows, it’s important to think about not only the solvents you use but also how you apply them. Paper towels, napkins, and washcloths are too abrasive and can scratch the surface. Lens tissues are specifically designed for cleaning optics, preventing lint from sticking to the window and scratching its surface. Some lens tissues come pre-saturated with solvent, while others are dry and need to be soaked in solvent before they are used. Don’t use a dry lens tissue on your optics; it can leave behind scratches.

Keep Dust, Oils, & Bacteria Out with Protective Gloves

Even freshly washed hands can leave behind oily fingerprints. Gloves help protect your sapphire windows from unnecessary dirt, oil, and bacteria on your hands, while also protecting your hands from chemicals. We recommend latex or nitrile gloves while working with your optics.

Consider Your Cleaning Environment

Gloves aren’t the only precaution you should take in the lab. A clean, sanitized workspace with the proper equipment is important to avoid dangerous or costly mistakes. Make sure you have enough light and space to complete the cleaning process. When cleaning smaller sapphire windows, consider using a magnifier to prevent accidental rough handling.

Cleaning Methods

Once you’ve gathered your materials, you’re ready to begin the cleaning process. There are two primary methods of cleaning sapphire windows: The Drop & Drag Technique and The Swab Technique

The Drop & Drag Technique

The Drop & Drag Technique is best for unmounted, flat optics with enough depth to elevate them above surrounding surfaces. In this cleaning method, you will need to identify the designated area where the solvent will be applied; this should be the part of the window with visible stains or scuffs. Remember, it’s best to avoid cleaning with solvents unless there is a visible mark.

Once the contaminated area has been identified, take a clean lens tissue and hover it just above the optic. Next, add a drop of solvent to the top of the tissue, aiming for the contaminated area. This will cause downward pressure, forcing the tissue and window to meet. The optic should be in a stable position so that, when this pressure is applied, the optic does not shift or move. Once the tissue has made contact with the window, gently drag it across its surface, toward the closest edge.

The Swab Technique

The Swab (or Brush) Technique works best for small, mounted, or curved optics and requires a pair of forceps or tweezers. As with the Drop & Drag Technique, start by identifying the specific area that needs to be cleaned. Then, take a clean lens tissue and fold it to be around the same size as your window. The excess edges will be clamped or held by forceps or tweezers. Be careful when folding the tissue; make sure the folded surface doesn’t come into contact with your fingers or forceps. Additionally, to avoid streaking, ensure that the folded surface is straight and taut.

After the lens tissue has been folded and attached to your forceps or tweezers, add a few drops of solvent to the tissue. The tissue should be saturated, but not dripping. Then, carefully wipe the lens tissue across the window’s surface, slowly rotating the tissue as you go.

Tips for Handling Sapphire Windows When Cleaning

To summarize, here are our top tips and best practices to consider when cleaning your sapphire windows.

Be Gentle

Sapphire windows, especially coated ones, are tough but not indestructible. Use soft motions and gentle tools to avoid scratching the surface or damaging coatings.

Take Your Time

Rushing through the cleaning process can lead to mistakes. Carefully apply each cleaning method to ensure all contaminants are removed, and don’t forget to let solvents evaporate completely before reusing the window.

Keep It Clean

A clean workspace makes all the difference. Any dust or dirt in your cleaning area could undo your efforts, so ensure that your tools and environment are spotless before handling sapphire windows.

Have questions? Contact us! Whether it’s coated or uncoated sapphire windows, high-temperature applications, or any other precision optic, we’re your go-to for the highest-quality products and expert advice.