How to Care for Hand Blown Glass: Cleaning, Storage and What to Avoid
Hand blown glass is not fragile in the way people assume. A well-made piece — properly annealed, blown from quality recycled or raw glass — will outlast most of the other objects in your home. But it does have specific requirements. The enemies of hand blown glass are not impact and breakage as much as they are temperature shock, chemical exposure, and the dishwasher.
This guide covers everything you need to know to keep hand blown glass in good condition for decades — and explains the reasons behind each recommendation, so you understand not just what to do but why.
Understanding What Hand Blown Glass Is — and Why It Behaves Differently
Before covering care instructions, it helps to understand what makes hand blown glass different from mass-produced glass.
Machine-made glass is produced under controlled conditions — perfectly even wall thickness, consistent composition, and a cooling process calibrated for uniformity. Hand blown glass has slight variations in wall thickness, minor differences in composition (especially when made from recycled glass), and a cooling curve that, while controlled through annealing, is less mechanically precise.
These variations are not weaknesses. They are the signature of the handmade process. But they do mean that hand blown glass responds to stress — thermal, mechanical, and chemical — slightly differently from uniform machine-made glass. Understanding this helps explain why the care rules exist.
Cleaning Hand Blown Glass
Always Hand Wash — Never the Dishwasher
This is the single most important rule for hand blown glass. Dishwashers are hostile environments for artisan glass in three ways:
• Temperature cycling: Dishwashers expose glass to rapid temperature changes — hot wash, cold rinse, hot dry. Hand blown glass with slight wall thickness variations is more susceptible to thermal shock cracking than uniform machine-made glass.
• Detergent chemistry: Dishwasher detergents are alkaline and abrasive at a microscopic level. Over repeated cycles, they etch the surface of glass — removing the natural shine and creating a permanent cloudy appearance called 'etching.' This damage is irreversible.
• Physical impact: Glasses shift and knock against each other and the dishwasher rack during cycles. The irregular forms of hand blown glass make them harder to secure and more prone to contact damage.
Hand washing in warm — not hot — water with a mild dish soap is all that is needed. Wash one piece at a time if possible. Rinse thoroughly and dry with a soft lint-free cloth rather than leaving to air dry, which can leave water spots.
Water Temperature for Washing
Use warm water — approximately 40°C (104°F) — not hot. Pouring near-boiling water into a cold glass, or washing a warm glass under cold water, creates a temperature differential between the inner and outer glass surfaces. This differential creates internal stress. In most cases, nothing happens immediately. Over repeated exposure, micro-cracks can develop that eventually cause the piece to crack or shatter.
The practical rule: if the water is uncomfortable to hold your hand in, it is too hot for your hand blown glass.
Removing Stubborn Deposits
Hard water leaves calcium deposits — white, chalky marks — on glass that simple washing does not remove. For hand blown glass, use a solution of equal parts white vinegar and water. Soak a soft cloth in the solution and wrap it around the affected area for a few minutes before rinsing. Do not use abrasive scrubbers or scouring pads — these scratch the glass surface permanently.
For the inside of narrow-necked pieces like jugs and decanters, a soft bottle brush works well. Avoid metal brushes or anything with a hard abrasive surface.
Cloudy Glass — Causes and Solutions
Cloudy hand blown glass typically has one of two causes:
• Water spots from hard water or air drying: These can usually be removed with the vinegar solution described above.
• Detergent etching from dishwasher use: This is permanent surface damage. The glass is not broken, but the surface clarity cannot be restored. This is the primary reason dishwasher use damages hand blown glass — and why it must be avoided from the start.
What to Store Hand Blown Glass In — and How
Storing Tumblers and Glasses
Store hand blown tumblers and glasses right-side up — not upside down. Storing glasses upside down is common practice for hygiene, but for hand blown glass with slightly uneven rims, it places the weight of the glass on the most delicate edge. Over time, stored upside down on a hard shelf, the rim can develop chips or micro-fractures.
If storing upside down is preferred for hygiene reasons, line the shelf with a soft cloth or rubber shelf liner to cushion the rim.
The same storage principles apply to all hand blown pieces — browse the full range of hand blown glass tumblers, jugs, and bowls to understand the variety of forms that need care.
Storing Stemmed Glasses
Stemmed hand blown glasses — wine glasses, goblets, champagne flutes — are most vulnerable at the stem. The stem is the thinnest and most structurally challenged part of the piece. When storing multiple stemmed glasses together, do not allow them to lean against each other stem to stem. Each glass should stand independently, with enough space that they do not contact each other when the shelf is accessed.
Dedicated stemware storage racks — where each glass hangs by its base from a slot in a rack — distribute the weight correctly and prevent contact between pieces. These are a worthwhile investment for frequently used hand blown stemware.
Wrapping for Long-Term Storage or Moving
If hand blown glass pieces need to be stored long-term or moved, wrap each piece individually in soft paper or bubble wrap. Never wrap two pieces together sharing a single layer of paper — if they knock against each other through the wrapping, they can chip. Newspaper ink can transfer to glass and is difficult to remove — use plain newsprint or tissue paper instead.
Stand wrapped pieces upright in boxes rather than laying them on their sides. Fill gaps with crumpled paper to prevent movement. Mark boxes clearly as fragile.
Temperature and Environment
Avoiding Thermal Shock
Thermal shock occurs when one part of a glass object changes temperature significantly faster than another. The resulting expansion or contraction differential creates internal stress that can crack or shatter the glass.
Situations to avoid:
• Pouring boiling liquid directly into a cold hand blown glass — allow the glass to reach room temperature first, or pour a small amount of warm liquid in first to temper it.
• Taking a cold glass directly from the refrigerator and filling it with a hot beverage.
• Washing a warm glass under cold water.
• Placing hand blown glassware in the freezer — the glass can crack as it cools unevenly.
• Leaving glass in a hot car, then bringing it immediately into an air-conditioned space.
The rule of thumb: change the temperature of hand blown glass gradually. Never subject it to sudden temperature extremes in either direction.
Direct Sunlight — Good and Bad
Hand blown glass, particularly colored glass, looks extraordinary in direct sunlight — it refracts and scatters light in ways that are genuinely beautiful. There is no harm in displaying hand blown glass where sunlight reaches it. The color in glass is structural — it will not fade in sunlight the way dyes and pigments do.
The one caution: direct sunlight on a glass surface can focus light in ways that concentrate heat on whatever surface the glass is sitting on, or on objects near it. This is more relevant for thick, curved, or heavily colored pieces. It is not a reason to keep glass out of sunlight — just something to be aware of in very specific circumstances.
Colored hand blown glass vases are particularly striking in sunlight — see examples in the hand blown recycled glass vases collection.
Using Hand Blown Glass for Food and Drink
Is Hand Blown Glass Food Safe?
Hand blown glass made from standard borosilicate or soda-lime glass is food safe. The glass itself is chemically inert — it does not leach into food or drink, and it does not react with acidic beverages like wine, juice, or vinegar-based dressings.
The exception to note: some decorative pieces — particularly older or very inexpensive pieces — may have metallic decorations painted onto the surface (gold or silver rims, for example). If these decorations are fired onto the glass correctly, they are food safe. If they are applied as a cold paint or coating, they may not be. When in doubt, contact the studio or maker directly. For pieces from reputable studios using food-safe processes, this is not a concern.
For details on how Kitengela Glass sources and processes its recycled glass — and why it is food safe — visit the recycling and materials page.
Hot Liquids
Standard soda-lime hand blown glass — the type used in most artisan glassblowing studios working with recycled glass — is not designed for hot beverages in the way that borosilicate glass (used for laboratory glass and some kitchen glass) is. Pouring very hot liquids — boiling tea, coffee straight from the pot — into a cold soda-lime glass creates thermal shock risk.
Warm liquids are fine. The practical test: if you can comfortably hold the liquid in your cupped hands, it is within the safe range for hand blown soda-lime glass. Beverages at or near boiling temperature should be allowed to cool slightly, or the glass should be tempered first by adding a small amount of warm liquid.
Microwave Use
Do not use hand blown glass in a microwave. The uneven wall thickness of hand blown pieces creates uneven heat absorption in microwave use, which produces internal stress. Additionally, any metallic elements in the glass — which can be present in colored recycled glass depending on the original material — can cause arcing in a microwave.
Repairing Chipped Hand Blown Glass
Minor chips on the rim or base of a hand blown glass piece can sometimes be polished smooth by a professional glass polisher — this removes the sharp edge without removing significant material. The piece will no longer be identical to its original form, but it can be made safe to use again.
Chips on the body of a piece — not on functional surfaces like rims — are purely cosmetic. They do not affect the structural integrity of the piece and do not need to be treated.
Cracked glass cannot be repaired to food-safe standard. A crack that goes through the wall of a glass creates a surface that cannot be fully cleaned and that will continue to propagate under thermal and mechanical stress. A cracked piece should be retired from use. It can still function as a decorative object if the crack is stable and the piece is not subjected to further stress.
Quick Reference — Do's and Don'ts
✅ Hand wash in warm water with mild soap
✅ Dry immediately with a soft lint-free cloth
✅ Store tumblers right-side up on cushioned surfaces
✅ Allow temperature changes to happen gradually
✅ Use vinegar solution for hard water deposits
✅ Handle by the body, not by the rim or stem
❌ Never put in the dishwasher — etching damage is permanent
❌ Never pour boiling liquid into a cold glass
❌ Never use in the microwave or freezer
❌ Never use abrasive scrubbers or scouring pads
❌ Never store stemmed glasses leaning against each other
❌ Never use harsh chemical cleaners or bleach
All hand blown glass at Kitengela Glass is made from 100% recycled Kenyan glass and annealed slowly to minimize internal stress — producing pieces designed for daily use, not just display.