Borosilicate Glass Sizes: Buying Tubing & Rod for Pipe Making

What glass do you need to make pipes?

This is the single most important thing to understand before buying glass. COE 33 isn't a brand — it's a specification. Simax, Schott DURAN, and the original Corning Pyrex 7740 / Kimble KG-33 are all COE 33 formulations and are mutually compatible at the torch. You can fuse any of them together without the join cracking under thermal stress.

One confusion trips up beginners constantly: the "Pyrex" brand sold in kitchenware stores today is soda-lime glass, not borosilicate. When Corning sold the Pyrex brand for consumer goods, the new owner switched to cheaper soda-lime. Lab-grade Pyrex 7740 and Kimble KG-33 are still true borosilicate, but if you pick up a Pyrex measuring cup at a thrift store hoping to melt it, you'll be working with the wrong glass. Always buy from a reputable glass supplier and confirm "COE 33 borosilicate" in the product spec before ordering. For all of this to make sense in the context of your whole setup, see our guide to borosilicate glassblowing for beginners.

How is glass tubing measured?

The industry groups wall thickness into four practical tiers. Knowing these tiers tells you whether a tube is suitable for a given pipe form before you even pick it up:

The market often describes quality in terms of wall thickness: "5 mm glass," "7 mm bong," "9 mm thick." These refer to wall thickness, not OD. A 38 mm OD / 5 mm wall water-pipe tube and a 38 mm OD / 7 mm wall tube are both 38 mm bong tubes — but the 7 mm version is noticeably heavier and more premium. Understanding the difference means you can read supplier listings accurately and spec the right glass for any order.

For a deep dive into all the other tools and materials you need alongside your glass, see the full beginner equipment rundown.

What size tube do you use for spoons and small dry pipes?

The spoon is almost always the first pipe a maker learns, and for good reason — it demands the core vocabulary of heat control, gathering, shaping, and hole-burning in a compact form. Choosing the right tube OD matters here because the bowl diameter is largely determined by your starting tube. Too small and the bowl feels toy-like; too large and a beginner's heat management quickly gets overwhelmed.

• 25.4 mm (1") x 4 mm heavy-wall — the classic beginner spoon tube. Manageable OD, sturdy wall, makes a comfortable mid-size bowl. Stock this first.
• 32 mm (1-1/4") x 4 mm heavy-wall — a slightly bigger bowl, popular for the "fatboy spoon" look. Great second tube to add once your heat management is solid.
• 8–12 mm x 1.5–2.2 mm — the chillum / one-hitter range. Small, fast to work, good practice glass for learning basic pulls and seals.
• 12–14 mm medium-wall — necks and mouthpieces on spoons and sherlocks. Often pulled from slightly larger tube or worked down from the body tube in the same session.

If you are making sherlocks (curved spoons), you're working with the same bowl tube — the curve comes from re-heating and bending the neck after it's formed, not from a different diameter. The progression from spoons to sherlocks is covered in depth in our guides and in Volume 1, which shows every spoon-making step on-camera from glass selection through finished piece.

What size tube do you use for downstems, joints, and couplers?

Joint sizing is one of the most confusing areas of glass specification, because the "10/14/18" numbers describe the finished ground inner bore — not anything you'd order from a glass supplier as raw tube. Here's how to think about it:

• 10 mm joint — the smallest standard, common in mini rigs and dab pipes. Requires a narrow tube to pull from.
• 14.5 mm ("14") joint — the most common mid-size joint, found on the majority of water pipes. Often called "14mm" colloquially.
• 18.8 mm ("18") joint — the large standard, typical on bigger bongs and beakers. More airflow, heavier builds.

Pulling your own joints from raw tube is an intermediate-to-advanced skill — it requires a mandrel or precision grinding to achieve a true ground seal. Most pipe makers starting out buy pre-made COE 33 joint fittings from a supplier (Mountain Glass Arts and Wale Apparatus both stock them) and weld them into their builds. This lets you focus on the pipe body and bowl work while you develop the skills to pull clean joints later.

Downstem tube — the tube that carries smoke from the bowl down into the water — typically runs 19–22 mm OD at heavy wall, long enough to angle into the water chamber at the correct depth. The exact length depends on the body tube's water-chamber depth, which is why downstems are often cut to fit during the build.

What size tube do you use for water pipes and bongs?

Water pipes are where glass sizing decisions compound: you need a body tube, a neck tube, a downstem, and either pulled or pre-made joints, all in compatible COE 33. Getting the proportions right matters for both aesthetics and function — a body tube that's too narrow restricts airflow; one that's too wide is hard to heat evenly for a beginner. The 38 mm standard hits the sweet spot.

• 32 mm OD, heavy-wall — mini bong body. Faster to make, less glass to manage. Good for a first water-pipe attempt.
• 38 mm OD, 4–5 mm wall — the dominant mid-size bong tube. Most production water pipes use this diameter. Widely stocked by every major supplier.
• 50 mm (2") OD, 5–7 mm wall — large "fatboy" or beaker tube. Premium feel, significant weight. Needs a torch capable of handling the mass — see our guide on choosing a torch big enough for heavy-wall glass before stepping up to this size.
• 19–22 mm OD, heavy-wall — downstem and neck tube. Sized to run into the body and seal cleanly at the joint.

Thick-wall vs. thin-wall borosilicate — which should you use?

From a practical maker's perspective, wall thickness affects your work in two ways: how the piece behaves while you're working it, and how it holds up once it's sold.

While working: thick glass holds heat longer after you pull it from the flame, which gives you more time to shape, gather, and manipulate before it stiffens. This sounds like an advantage for beginners, but it also means you need a hotter, more capable torch to get heavy-wall glass up to working temperature in the first place. Thin glass reaches temperature quickly and responds fast — which is actually more forgiving for a beginner on a smaller torch, though the finished piece will feel cheap.

Once sold: buyers feel the difference immediately. A 3 mm wall pipe feels noticeably lighter and more fragile than a 5 mm wall pipe of the same OD. Premium pipes in the market — the pieces selling for $80–$300 — are almost universally 5 mm wall or heavier. If you're making pieces to sell rather than just to practice, starting on heavy wall trains you to work at the quality level the market rewards.

The practical recommendation: practice on medium-wall (1.8–2 mm) if your torch is small and your heat management is still developing. Move to heavy-wall (3–4 mm) as soon as your torch can handle it. Never sell thin-wall pipe work — it damages your reputation before it's even built. If you need to upgrade your heat source, our guide to choosing a torch big enough for heavy-wall glass covers every option by budget.

What about rod — punty and color?

The punty is the workhorse of the torch station — a solid rod of clear COE 33 glass you melt onto the base of a piece so you can hold it in the flame without burning your fingers. When you see a glassblower turning something in the flame with a long rod, that's the punty. Having both 4 mm (for smaller pieces and stringer pulls) and 6 mm (for heavier pieces) in stock means you're covered for most work.

Thin clear rod — 2–4 mm — is also pulled into stringer: long, hair-thin threads of glass used for line work, trailing, and surface decoration. Once you're pulling stringers, you're entering the decorative side of the craft.

Color rod is where you start spending real money. The major brands are:

• Northstar Glassworks — the industry benchmark for predictable, consistent color. Wide range, excellent documentation of each color's behavior. See Northstar's color catalog for the full line.
• Glass Alchemy (GA) — known especially for silver-fuming reactive colors and striking glasses. Used extensively by artists doing color-changing glass work.
• Trautman Art Glass (TAG) — well-regarded for borosilicate-compatible color rods, good COE 33 compatibility across the range.
• Momka's Glass — smaller producer with dedicated following for specific color families.

Start with one or two inexpensive Northstar colors and practice how color rod moves compared to clear tube before committing to a large color order. Color rods handle differently from clear glass — they have different viscosities and some colors behave unexpectedly in the flame — and the best way to understand them is at your own torch rather than from a spec sheet.

What glass should a beginner stock — and where do you buy it?

Here's a concrete starter-stock table covering both the spoon-pipe essentials and the additional glass you'll need when you step up to water pipes:

Clear glass brands: Simax is the most widely stocked COE 33 tubing in the US market and is the default at most suppliers. Schott DURAN is the European benchmark — excellent quality, slightly less available in the US. Corning Pyrex 7740 and Kimble KG-33 are both COE 33 and fully compatible. Cheaper Chinese-import tubing is available and some of it is fine, but test COE 33 compatibility against a known Simax or Schott piece before ordering in bulk — not all import glass is accurately labeled.

Where to buy:

• Mountain Glass Arts — the largest dedicated lampworking supplier in the US, widest selection of Simax tubing in every OD and wall class. First stop for most pipe makers.
• Wale Apparatus — excellent heavy-wall Corning Pyrex tubing stock; well-regarded for quality control and customer service.
• ABR Imagery — focuses on boro and color glass; popular with pipe makers for color rod selection alongside clear.
• Glass House Supply — competitive on price, good range of tube and rod for beginners.
• Frantz Art Glass — long-established supplier, good Simax stock.
• Ed Hoy's International — broad inventory including specialty tubing.

Buying local from a lampworking club or regional supplier can also get you started faster and lets you see what you're buying before committing to a full order. Once you know your sizes and brands, online ordering scales better — but your first purchase benefits from hands-on comparison.