Chapter 1: Drum Types & Bungs — UN Markings & Hazard Labels

Created by Sarah Choi (prompt writer using ChatGPT)

Drum types & bungs — UN markings & hazard labels (for prop concept artists)

This article is a depiction guide for barrels and drums used with hazardous and industrial materials. It translates real packaging, closures, markings, and handling cues into visual language that reads clearly in concept art and survives the handoff to production. It does not teach handling or compliance; when in doubt, avoid prescriptive instructions and focus on observation. The emphasis throughout is on believable silhouettes, surface logic, label placement, and the story told by valves, gauges, PPE and surrounding set‑dressing.

Drums versus barrels: vocabulary, scale, and silhouette

In industrial scenes the word “drum” is standard, although people casually say “barrel.” The iconic unit is the 55‑gallon or 200‑liter drum at roughly knee‑to‑chest height for an adult, with a diameter that comfortably sits four‑up on a square pallet. Steel drums present crisp cylindrical shells with two reinforced edges called chimes and two or three shallow ribs called rolling hoops; these hoops prevent denting and provide grip when a drum is tipped and rolled. Plastic drums carry softer profiles with molded handles and an L‑ring or double‑ring at the top. Fiber (“cardboard”) drums show kraft paper spirals, metal rings, and a slightly thicker wall. Recognizable proportions are part of the silhouette read: steel closed‑head drums feel taut and crisp; open‑head drums look fractionally taller once the ring and lid are present; plastic tight‑heads have domed tops with bung bosses that stand proud.

The four families: steel, plastic, fiber, and salvage/overpack

Steel drums dominate where heat resistance, vapor barriers, and durability matter. Closed‑head (tight‑head) steel drums have a permanently attached top with two threaded openings, while open‑head drums accept a full‑diameter lid and a closure ring. Plastic drums are usually high‑density polyethylene; tight‑head versions have two molded bung bosses, and open‑head versions accept a lid with a lever‑lock band. Fiber drums package solids and lab packs; they are lighter, cheaper, and read as less threatening. Salvage and overpack drums are oversized containment shells, usually bright yellow poly or heavy steel, designed to swallow a damaged or leaking drum; their scale is intentionally a size up, and their ring hardware appears chunky and overbuilt. When dressing a scene, mixing two or three families instantly tells a story about logistics, cost constraints, and risk.

Open‑head versus closed‑head: anatomy and closure logic

Open‑head drums communicate access for solids, sludges, and sorbents. You will always see a circular lid with a compressible gasket and either a bolt‑ring that requires a wrench or a lever‑lock band with a positive latch and safety pin. Closed‑head drums communicate liquids or viscous materials that are dispensed through small openings. Their heads carry two threaded fittings: a larger one, often referred to as the “two‑inch bung,” and a smaller companion, often called the “three‑quarter‑inch bung.” These fittings are set on opposite sides of the crown or within a shallow sump so that draining leaves minimal residue. In plastic tight‑heads these appear as molded bosses with female threads; in steel they appear as pressed‑in flanges with removable plugs. A convincing depiction shows thread caps flush or very slightly recessed, with a secondary tamper cap or tear‑tab seal when the product is new.

Bungs, plugs, gaskets, and the tools that touch them

The term “bung” refers both to the threaded flange in the drum head and to the removable plug that seals it. Steel drums typically use straight pipe threads with square or hex drive sockets in the plug; plastic drums often use coarse buttress threads with broad flats for a wrench. Plugs seat against a gasket, and gasket material telegraphs chemical compatibility in the prop’s backstory: black nitrile reads as hydrocarbon‑friendly, off‑white EPDM suggests oxidizers and aqueous solutions, and darker fluoropolymer gaskets imply aggressive solvents and higher temperatures. New drums frequently carry a tamper‑evident capseal—thin metal or plastic that crimps over the plug and tears away—so remnants of a torn ring around the plug read as “opened today.” The hero close‑up can include a purpose‑built bung wrench with multiple prongs, a torque seal paint swipe bridging plug to flange, or witness marks from overtightening. A vented plug with a tiny sintered bronze disc reads as pressure equalization without turning your scene into a pressure vessel set piece.

Valves, faucets, pumps, and adapters: making liquid movement legible

When drums are in use, the plugs are often replaced by dispensing hardware. A compact brass drum faucet on the small opening communicates low‑viscosity liquids; a quarter‑turn ball valve with a rigid spout communicates faster flow; and a robust gate valve reads as viscous or particulate content. Hand pumps are common and highly readable: a cast‑aluminum rotary pump with a curved discharge, a lever‑action piston pump with a long handle and riser tube, or a squeeze‑bulb siphon dangling into a secondary container all add kinetic intent. Adapters tell material stories. A stainless nipple to hose barb with a worm‑drive clamp implies water‑based chemistry; a black iron fitting with PTFE tape peeking at the joint implies hydrocarbons; and a clean polymer quick‑connect suggests food or pharma. For advanced reads, a flame arrestor cap or spark‑resistant bronze faucet paired with a grounding clamp to a building earth point nails flammable‑liquid handling without ever instructing the viewer how to do it.

Gauges, vents, and collapse cues

Drums are not pressure vessels, but they breathe. A subtle dish‑in on the flat of a steel head (“oil‑canning”) implies vacuum after cooling; a bulged head suggests internal gas generation or heat. Plastic drums tell level with deformation and scuff patterns; you can also paint a translucent level stripe or a molded sight‑gauge tube fixed with two small fittings. A simple low‑profile pressure/vacuum relief cap in the small opening reads as vapor management in hot climates. Do not depict complex bourdon or digital gauges unless your story justifies process integration; drums themselves rarely carry them beyond a vent cap or a sight accessory.

Interiors, linings, and invisible cues

A steel drum’s inside may be unlined, which oxidizes and smells metallic once opened, or lined with a pale epoxy‑phenolic coating that looks enamel‑smooth and telegraphs food, pharma, or water‑borne content. A black, glossy lining communicates aggressive chemistry. Plastic interiors carry the same color as their exterior and often show mold parting lines and a slight orange‑peel texture. Fiber interiors are raw spiral‑wound kraft. Artists can imply interiors without showing them by using stampings and stencils on the exterior that reference lining type, lot codes, and rinse status.

The UN packaging mark: decoding the stamp so you can fake it believably

Every performance‑tested drum carries a code that looks like a compressed sentence. The first block identifies the packaging type and material; for drums “1A1” signals a steel closed‑head, “1A2” a steel open‑head, “1H1” a plastic closed‑head, “1H2” a plastic open‑head, and “1G” a fiber drum. The next block signals the performance level: X for the most severe, Y for medium, and Z for the least severe. For liquids, this is followed by a maximum specific‑gravity number and then a hydrostatic test pressure in kilopascals; for solids and combination packagings, you instead see a maximum gross mass in kilograms and an “S” that flags the solids test. The tail of the mark gives the year of manufacture, the country authorizing the test, and a manufacturer code. An example that reads clean on camera is “1A1/Y1.8/300/24/USA/M1234,” which says “steel closed‑head, medium performance, tested to a liquid density of 1.8 and a hydrostatic pressure of 300 kPa, made in 2024 in the USA by manufacturer M1234.” If your drum is for a powder in an open‑head steel body, a plausible stamp would read “1A2/Y150/S/24/USA/M1234,” which communicates a 150‑kilogram solids rating with the “S.” Salvage packagings have their own variant marks and often carry the word “SALVAGE” plainly; overpacks used to group multiple packages carry “OVERPACK” near the shipping description. For fiction, keep the structure, alter the numbers and maker code, and you will retain credibility while avoiding real regulatory claims.

Hazard labels, transport placards, and GHS pictograms: what goes where

Industrial drums carry two parallel labeling languages. The transport language uses square‑on‑point diamonds with bold numerals to indicate hazard class, such as a red flame on a red diamond with the number 3 for flammable liquids or a black‑over‑white split diamond with test tubes attacking a hand and a bar for corrosives in class 8. This transport label sits near the proper shipping name and the UN four‑digit identification number, which is often repeated in black text on a contrasting panel or within its own small orange or white rectangle depending on region and carrier. The workplace language uses red‑bordered white diamonds with simplified pictograms for flammability, toxicity, corrosivity, oxidizing potential, gases under pressure, environmental hazard, and health hazard. A realistic drum shows both systems coexisting on a single main label panel, accompanied by supplier information, product identifier, and numbered hazard and precautionary statements in a font that reads at arm’s length. For liquids, add two vertical “This Way Up” arrows to boxes and small packages, but not to drums lying horizontally. For marine pollutant stories, add a small fish‑and‑tree environmental mark near the transport label. For limited‑quantity narratives, a black‑and‑white diagonal diamond tells a cost‑saving small‑shipment tactic and immediately looks like logistics, not danger. Smudges, UV‑faded reds, torn corners, and hand‑written lot codes make labels feel handled and old without changing their meaning.

Secondary containment, pallets, and the choreography of handling

Surrounding hardware turns a static cylinder into a working prop. Two‑drum and four‑drum spill pallets are molded plastic platforms with grating tops and a deep sump; they read as industrial safety the instant a drum sits on them. A yellow or black drum dolly communicates mobility and adds believability to boutique labs and workshops. A curved‑back two‑wheeled drum truck shows how a single worker tips and walks a drum; its nose plate shows crescents or straps that cradle the cylinder. Palletized drums show steel or polyester banding with corner protectors and a shrink‑wrap “neck” at the top for forklift grab clearance. Forklift scars on chimes, crescent scuffs where a drum was rolled, and a single dent at a hoop instantly age a set. Overpack drums, when present, are always slightly too large for their occupant and frequently have stencil text that says “LEAKING” or “DAMAGED” along with a date and initials.

PPE and the human scale of hazard work

The people around drums define the tone of the scene. Light operations show nitrile gloves, splash goggles, and perhaps a face shield during dispensing. More severe scenes add chemical suits with taped seams at gloves, boots with raised toe caps, and a respirator or hood. The suit fabric tells the story: a white non‑woven reads as general lab splash protection, a bright laminate with a matte finish reads as solvent barrier, and a heavier glossy suit reads as corrosive duty. Hard hats with ear protection, reflective vests near forklifts, and small disposable earplugs in pockets place the set firmly in a working facility. A grounding clamp and cable attached to a drum conveys flammable‑liquid safety without words. An eyewash bottle or plumbed station within sight completes the human‑safety triangle with spill kits and gloves.

Surface language: dents, stains, and torque‑seal

Drums accumulate history at edges and openings. Chimes take the hits, picking up bright metal crescents where paint has flaked from a forklift nick. Rolling hoops collect grime and dust, creating three dark equators on a steel profile. Around bungs, dried resin flowers out from the plug if the contents were sticky; otherwise a faint fan of drip marks below the small opening hints at dispensing. Torque‑seal lacquer creates a thin colored line from plug to flange; if broken, show a jagged gap. Plastic drums sun‑fade unevenly, especially on the top and the upper portion of the sidewall. Fiber drums fuzz and delaminate at edges, and the inner paper spiral becomes legible at chips. Avoid clichéd radioactive green ooze; use restrained, realistic staining to sell authenticity.

Label placement, typography, and camera read

A single clean label panel is more readable than a collage. Place the main transport label and UN number on the “show” side with the proper shipping name underneath, then cluster your GHS pictograms and workplace text nearby. Large visual cues belong near the top third so they are visible in clusters. Use sans‑serif, bold condensed faces for UN numbers and shipping names, and a neutral sans for the smaller regulatory text. Keep the red diamonds crisp and the class numerals heavy. On plastic drums, add molded legal text in tiny raised lettering near the upper ring; this is the right place to put your fictional manufacturer and mold date clock.

Region flavor without a compliance rabbit hole

You can imply geography without memorizing rule books. European settings read with orange plates for UN numbers on vehicles, metric units on labels, and multi‑language hazard statements. North American scenes read with imperial units, EPA “hazardous waste” accumulation labels on waste drums, and bolder, larger DOT diamonds. Maritime context reads with a small “marine pollutant” mark and salt‑scuffed surfaces. All three regions accept the same broad visual logic: diamonds, UN codes, and a manufacturer’s mark. Use that consistency to keep your designs portable across settings.

Integrating drums into valves, gauges, and process set‑pieces

The moment a drum hooks into a process, the fittings matter. An adapter stack from a two‑inch opening up to a stainless quick‑connect tells a micro‑plant story. A heat band wrapped around a viscous‑product drum, with a small thermostat box and a power cable, communicates warming for flow. A short section of transparent hose with bubbles down to a glass beaker communicates sampling. A small inline sight glass or a magnetic stir plate next to an open‑head drum with a lined interior reads as bench‑scale formulation or cleanup. Keep gauges minimal on the drum itself and put your complex instrumentation on a small skid or wall panel behind it; that way the drum stays a drum, not a reactor.

Production notes: what concept artists should call out, what production must preserve

For concept artists, call out the drum family, head type, opening sizes, and any permanent hardware like a ring or pump. Include a decoded example of your UN mark so modelers can stamp it consistently, and specify the relative size and placement of hazard diamonds and the UN number in the label panel. If PPE is part of the story, call out the suit material finish and the respirator silhouette. For production artists, preserve the diameters, the count and spacing of hoops, the depth of the top crown, the bung boss heights, and the thickness and latch geometry of ring hardware so that lighting and contact shadows behave. Keep labels high enough to clear the top pallet deck and spaced to avoid mesh intersections with bands or dollies. When simulating use‑wear, confine the heaviest damage to chimes and hoop highs; avoid all‑over noise that destroys material reads.

Storytelling with stacks, clusters, and color

Color does heavy lifting. Steel drums often ship in deep blue, black, or neutral primer gray; plastic drums appear in blue, white, black, or natural translucent hues; fiber drums are tan with silver or black rings. A cluster of four blue plastic tight‑heads on a yellow spill deck with a few red flammable‑liquid diamonds reads instantly as chemical storage. Mixing one yellow overpack among a neat stack of black waste drums ramps tension without any text. A single white drum with a pristine label and a ground clamp in a cluttered shop frames it as the dangerous but vital feedstock amid benign paint and oil drums. Use color to guide the eye to the hazard story without shouting.

Fictionalization without losing credibility

To avoid real‑world claims, invent manufacturer names, lot codes, and model identifiers while preserving structure. Keep the UN four‑digit length and diamond shapes; change the numerals. Keep the packaging code cadence; change the year and maker code. Write plausible product names that imply function rather than named chemicals. The audience reads the rhythm as authentic even if every word is imaginary.

Quick reality checks before handoff

Before you ship your concept, check that your drum’s head type matches the story of the contents, that your bung hardware and any pump or faucet is compatible with the head type you chose, that your label panel does not collide with rings or bands, and that your PPE choices match the tone of the scene. If your drum ever lies on its side, rotate labels so the diamonds still read right‑way up; if it stands on a spill deck, let the grating pattern show in the contact shadow. One last swipe of torque‑seal, a scuff on the chime, and a faint drip under the small bung will do more for truth than any amount of sci‑fi greeble.

Depiction‑only note: This article focuses on visual accuracy for entertainment design and does not substitute for standards or training. Avoid copying real compliance text verbatim, and do not instruct characters to bypass safety equipment. Let the forms, labels, and fittings tell the story.