6- Zinc sheet metal basics with a special note about galvanized steel.
There are two different basic classes for decorative sheet zinc.
The most typical, alloys zinc with a little bit of Titanium, which gives it strength and rigidity, and a resistance to dents and dings. This is typically used for tables and decorative panels, sometimes referred to as “bright” or “natural” zinc.
Another, lesser-used alloy is soft or dead soft sheet, which excludes Titanium, making it very malleable. And as a side note, this removal of the stiffer alloy component and subsequent reference as “soft” is common with many metals. Dead soft material is historically used for roof flashing, and although it is easy to work with mallets and hammer tooling, it receives and holds dents and dings more easily. It is also usually available in much narrower widths, because it is fabricated primarily for flashing details.
At this point, I must talk about galvanized sheet. Hot-dip galvanizing is the process of immersing iron or steel in a bath of molten zinc to produce a corrosion resistant, multi-layered coating.
It can have all kinds of nasty stuff in there as well that helps this surface hold up to harsh outdoor elements. It is STEEL, with a thin coating of zinc, so it fabs much differently than sheet zinc.
Do not use galvanized steel for food surfaces- this is a big no-no. It can and will rust over time, and it will release small nasty particles that could contaminate your food and cause big problems. Don’t do it! I’ve seen all sorts of instructions on the internet over the years, and it makes me want to outreach every time. Decorative elements are fine, but not for tops. Don’t do it!
Zinc sheet gauge, or thickness, works the same as with most gauges, but of course zinc sheets vary from standard wire gauge sizes and other sheet metal charts. In general, the higher the number gauge, the smaller the thickness.
Thinner sheets tend to oil can more, or ripple, while thicker sheets are harder to work and form, but resist rippling. Most commercially available sheets are in the 16-24 ga range.
When seeking the most commonly used thicknesses for sheet tables, look for a sweet spot with 22 gauge (.027”) or 20 gauge (.030”) which is roughly 1/32”. I like to use thicker sheets on bar tops, so a minimum of 16 gauge to 8 gauge (.125” or 3mm).
As a rule of thumb, I remember 16 gauge is roughly 1/16” of an inch, or .06”, and 20 gauge is half of that, or .03” (Both are older/less common sizes for shotguns). I can interpolate between those for approximate thicknesses, and I also know which direction the scale moves each way.
When looking for a maximum size that can be fabricated in sheet, this can be an elusive stat because each fabricator can spec lots of different sized materials, but if they can’t quickly figure the largest size or tell you how many seams a project will have, chances are they haven’t completed enough projects to know these limitations. Not everyone can fabricate pieces 10’ long without a seam, so do your homework to make sure you know what you’re getting before ordering.
In general, natural sheets come either 1 meter wide (39.4”) or 48” wide, and in lengths from 8’-10’, though most product is spooled in production and can be made as long as you can comfortably transport and install on site. The widest dead soft material I’ve used is 27”.
Width is generally the limiting factor. If you’re ordering sheet for a project, know that it may come rolled up in a box, leaving it more susceptible to damage. If several sheets are needed for a project, consider a pallet charge, where the distributor may be able to ship to you in a flat format, saving time unrolling and destressing the product that might be rolled in a box.
Remember that sheet must be cut and/or wrapped around your substrate, so as a rule of thumb, remove a minimum of 3.5” from both the length and width for a typical 1.5” substrate. As an example, an 8’ sheet can wrap a substrate 92.5” or less, so account for your edge material and design your project smaller, if possible.