Vacuum Glass is a new block added in Galacticraft 4.
The block can be used for making windows in your space bases. It has the appearance of 2 panes of glass sealed into a surrounding frame. It will automatically connect with neighboring blocks of the same type, to build larger shaped windows.
The connections the Vacuum Glass can make include T shapes, cross-overs, and corner blocks. Using alternating corner blocks, a long diagonal sheet of glass can be made. Use your imagination to make other shapes, for example octagonal chambers.
Vacuum Glass comes in three glass types - vanilla, clear, and strong - and two frame types.
The strong variety is explosion-resistant, and is also harder to break.
If placed next to water blocks, all three types of Vacuum Glass give clear views into the water. This can be used to build large water tanks, or underwater bases. (If the Vacuum Glass is placed without surrounding wall blocks, this can let you see clearly into the water from some unintended angles, like X-ray vision - you can see into the water from any angle on the side where the Vacuum Glass is positioned. To avoid this visual glitch, place solid blocks as walls around the Vacuum Glass frames when positioning the glass near water.)
There are two frame types: one is colorable with white as its default color, the other has the texture of a Tin Decoration Block.
The frame takes its color from a nearby Chromatic Applicator. Place a Vacuum Glass block in the Chromatic Applicator, mix a color, then apply the color to the block. All nearby Vacuum Glass blocks of that type should immediately change their frame color to match that chosen color. To have 2 different frame colors in your base, use 2 different types of Vacuum Glass.