The Bronze Age is a new tier of machinery added in the 4.0x iterations of GregTech, for Minecraft 1.6. It extends the early game phase, and forces players to actually work to get their Electric age IndustrialCraft and GregTech machinery.

The Bronze Age machinery are also known as Steam machines, because all but one of them consumes Steam as its energy source. This Steam is produced by the Small Coal Boiler and the High Pressure Coal Boiler. Note that Steam produced by Railcraft Steam Boilers is also a valid source of Steam for use in machines.

All Bronze Age (Steam) Machines share the following properties:

• They consume Steam as their source of energy.
• They function similarly to basic Electric machines.
• They do not catch fire or explode when exposed to rain.
• Their backsides are covered by a Steam Vent. This Vent must be left uncovered (they must face an air block), or the machine will cease to function after one process. The vent side can be changed with a Wrench.
• If their Steam supply is interrupted, their progress will pause but not be lost.

Most Steam machines are designed based on already known Electric machines, and use the same or similar recipe lists. However, they are much slower than their Electric counterparts.

• The Sturdy Grinder uses the same recipe list as the Universal Macerator, but with all outputs and byproduct chances halved. Output values for grinding items are not halved.
• The Steam-Powered Forge Hammer is used to flatten metal Ingots into metal Plates, similar to the Plate Bending Machine. However, the Steam-Powered Forge Hammer consumes 2 Ingots to create 1 Plate.
• The Steam Furnace works just like a regular or Electric Furnace.
• The High Pressure Steam Furnace works like the Steam Furnace, but cooks items faster and for less Steam.
• The Squeezing Extractor works like the regular Electric Extractor, and is the one machine actually required to advance to the Electric age. (Sticky Resin cannot be smelted into Rubber.)
• The Steam Compressor uses the same recipe list as the regular Electric Compressor.
• The Steam Smelter uses the recipe list of the Alloy Smelter.
• The Bronze Workbench is a sort of non-automatic Electric Crafting Table, akin to the old Redpower Project Table. It contains 16 Item slots, 5 Tool slots, a 3x3 Crafting grid, and several slots for a not-yet implemented crafting Plan system.

The Bronze Blast Furnace does not consume Steam. In stead, it consumes Iron and either Coal, Charcoal or Coal Coke to produce the Steel required to advance in to the Electric age. This is however a very slow process, and as such most players build several Bronze Blast Furnaces before advancing to the Electric age.

The High Pressure Steam Furnace and High Pressure Coal Boiler are both crafted using Steel in the place of Bronze. They are intended to form the top end of the Bronze Age, and the gateway into the Electric age. Additionally, (Automatic) E-Furnaces are now crafted using a High Pressure Steam Furnace, rather than an Iron Furnace.

1.7 Bronze Machines

The GregTech Alpha for Minecraft 1.7.2 includes a full suite of Steam-powered Bronze machines. They have similar math controlling them as the 1.6.4 machines. Below are three tables showing their Steam usage statistics. Note that these were tested using GregTech 5.00g and may not fully reflect the values of 4.08s.
Machines marked with a - do not exist in 1.6.

Steam Boilers

Boiler	Steam Output (Litres)	Output Frequency (ticks)	Output/tick (L/t)
Small Coal Boiler	150	25	6
High Pressure Coal Boiler	150	10	15
- High Pressure Lava Boiler	300	10	30
- Solar Boiler	150	25	6

Boiler Steam production rates did not change between 1.6 and 1.7.

Bronze Steam Machines

Machine	Steam / tick	Process Time (ticks)	Process Time (seconds)	Steam / Process (L)
Steam Alloy Smelter	- Recipe Specific -
Steam Compressor	2L/t	800	40	1600
Steam Extractor	2L/t	800	40	1600
Steam Powered Forge Hammer	- Recipe Specific -
Steam Furnace	4L/t	256	12.8	1024
- Steam Macerator	2L/t	800	40	1600

The Sturdy Grinder no longer exists in 1.7 as it was replaced by the Steam Macerator.

Although the Steam Alloy Smelter and Steam Powered Forge Hammer have recipe-specific processing times and steam consumptions, their Steam/tick consumption tends to be much higher than that of the other Steam machines. Many of their recipes consume 16 Litres of Steam/tick.

Steel Steam Machines

Machine	Steam / tick	Process Time (ticks)	Process Time (seconds)	Steam / Process (L)
- High Pressure Alloy Smelter	- Recipe Specific -
- High Pressure Compressor	6L/t	400	20	2400
- High Pressure Extractor	6L/t	400	20	2400
- High Pressure Forge Hammer	- Recipe Specific -
High Pressure Furnace	12L/t	128	6.4	1592
- High Pressure Macerator	6L/t	400	20	2400

The High Pressure Steam Machines are made of Steel, and function the same as their Bronze counterparts. However, they do so at twice the speed and consume Steam 3x as quickly, in total consuming 50% more Steam per operation.
Only the High Pressure Steam Furnace exists in 1.6.