Mill finish, degreased
For cap makers who lacquer and print in-house. Must be clean and dry for good lacquer adhesion.
Closure stock guide
3105 H14 / H16 Aluminium Sheet, Strip and Foil for Screw Caps
3105 is an aluminium-manganese-magnesium alloy rolled to about 0.15 – 0.5 mm and supplied in H14, H16 and H24 tempers as closure stock for roll-on pilfer-proof (ROPP) and screw caps on wine, spirits, water, oil and pharmaceutical bottles. Cap makers buy it for low earing, tight gauge control and a surface that takes lacquer and print evenly.
- Alloy
- 3105 (EN AW-3105)
- Tempers
- H14, H16, H24, H26, H18
- Gauge
- about 0.15 – 0.50 mm
- Earing
- about ≤ 3 – 4 %
Why 3105 is used for screw caps
A ROPP cap starts as a lacquered, printed sheet. Discs are blanked and drawn into a shallow shell, a liner is inserted, and the capping head on the filling line rolls the thread and the tamper-evident band onto the bottle neck.
That sequence asks a lot of the metal. It must draw without tearing, keep an even rim height (low earing) so the band forms correctly, be stiff enough to hold torque, and soft enough for the capping head to roll threads into it. 3105, with about 0.5 % manganese and 0.5 % magnesium, sits in the right place: stronger and stiffer than 8011 or 1100 at the same gauge, more formable than 5xxx alloys. 8011 remains common for lower-cost caps; 3105 is chosen where thinner gauge, higher torque or more demanding shapes are needed.
3105 chemical composition (wt %)
| Element | Limit |
|---|---|
| Manganese (Mn) | 0.30 – 0.80 |
| Magnesium (Mg) | 0.20 – 0.80 |
| Silicon (Si) | ≤ 0.60 |
| Iron (Fe) | ≤ 0.70 |
| Copper (Cu) | ≤ 0.30 |
| Chromium (Cr) | ≤ 0.20 |
| Zinc (Zn) | ≤ 0.40 |
| Titanium (Ti) | ≤ 0.10 |
| Others each / total | 0.05 / 0.15 |
| Aluminium | Remainder (about 96 – 99 %) |
Closure mills usually work to a tighter internal window than these registered limits, because small shifts in manganese, iron and magnesium change earing and work-hardening. For food and beverage contact, the alloy also meets the composition limits of EN 602.
Tempers and mechanical properties
| Temper | Tensile strength (MPa) | Elongation (min, thin gauge) | When to choose it |
|---|---|---|---|
| H14 | 150 – 200 | about 1 – 2 % | General ROPP caps; good balance of draw and stiffness |
| H24 | 150 – 200 | about 3 – 4 % | Lacquered stock; partial anneal gives more ductility at the same strength |
| H16 | 175 – 225 | about 1 % | Higher torque, thinner gauge, larger diameters |
| H26 | 175 – 225 | about 3 % | Stiffer lacquered stock with better formability than H16 |
| H18 | ≥ 195 | about 1 % | Stiff stock for shallow parts |
Ranges follow the EN 485-2 bands for thin 3105 sheet; closure specifications often narrow them (for example 160 – 190 MPa for H14) to keep capping behaviour consistent. Agree the window with the mill.
Because the lacquer and print are cured in ovens, the strength the cap maker sees is the after-bake strength. Ask for properties both as-rolled and after a simulated bake cycle that matches your line.
Earing, flatness and gauge tolerances
| Characteristic | Typical closure-stock requirement | Why it matters |
|---|---|---|
| Earing (cup test) | H14 about ≤ 3 %; H16 / H24 / H26 about ≤ 4 % | Uneven rim height spoils the tamper band and wastes trim |
| Thickness tolerance | about ±0.005 mm up to 0.25 mm; ±0.010 mm to 0.50 mm | Gauge variation changes draw depth and capping torque |
| Width tolerance | +0.5 / 0 mm up to 800 mm; +1 / 0 mm above | Feeding in printing presses and blanking |
| Longitudinal flatness | Wave height about 2 – 3 mm max | Lacquering and printing need flat sheet |
| Camber | about ≤ 5 mm | Straight feeding into presses |
| Surface | Free of oil stains, roll marks, scratches and inclusions | Visible on the finished cap |
Surface conditions available
Chromated or chrome-free pre-treated
A conversion layer that improves lacquer adhesion and corrosion resistance under the liner.
Clear lacquered both sides
Ready for printing; inside lacquer must suit the liner compound and product.
Coloured one side
Gold, silver, white, black, red, blue and custom shades outside, protective lacquer inside.
Lubricated (DOS)
A light lubricant film for drawing on some lines.
Supply range and packing
Typical supply
- Thickness
- about 0.15 – 0.50 mm; 0.20 – 0.25 mm is common for 28 – 31.5 mm ROPP caps
- Width
- Slit coil about 50 – 1500 mm; sheet about 500 – 1500 mm wide
- Coil inner diameter
- 75, 150, 200, 300, 350, 405 or 505 mm
- Sheet
- Cut to press size for sheet-fed lacquering and printing
- Packing
- Eye-to-sky or eye-to-wall on wooden pallets, moisture barrier film and desiccant
- Certification
- EN 10204 3.1 certificate with chemistry, tensile, earing and gauge results
Where 3105 closures are used
- Wine and spirits ROPP caps, including long "Stelvin-style" wine closures
- Mineral water, juice and soft-drink caps
- Edible oil and sauce bottle caps
- Pharmaceutical vial and syrup closures
- Cosmetic and perfume caps, and decorative shells
3105 is also rolled for other light-gauge products, such as shutter slats and PCB entry sheet, but closure stock carries the tightest earing and surface requirements.
References and standards
- EN 485-2 – Aluminium sheet, strip and plate: mechanical properties
- EN 573-3 – Chemical composition and form of wrought products
- EN 602 – Wrought aluminium products: chemical composition of semi-products used for articles in contact with food
- ASTM B209 – Aluminum and Aluminum-Alloy Sheet and Plate
- European Aluminium – Aluminium closures and packaging
3105 closure stock: frequently asked questions
Why use 3105 instead of 8011 for caps?
3105 is stronger at the same gauge, so caps can be thinner or hold higher torque. 8011 is cheaper and is widely used for standard caps.
What is earing and why does it matter?
Earing is the wavy rim formed when a disc is drawn into a cup, caused by directional properties in the sheet. Low earing (about 3 – 4 % or less) keeps the cap skirt even so threads and tamper bands form correctly.
Which temper should I order, H14 or H24?
H24 is common for stock that will be lacquered because it has more elongation at the same strength. H14 suits caps formed from bare or pre-treated stock.
What thickness is used for ROPP caps?
Usually about 0.20 – 0.25 mm for 28 – 31.5 mm caps, thicker for larger diameters or high-torque caps.
Is 3105 safe for food and drink contact?
Yes, when the alloy meets EN 602 and the inside lacquer and liner are approved for the product.
Need 3105 closure stock?
Send gauge, width, temper, earing limit and surface requirements. We will confirm the specification and a delivered price.
