Interleaving Powder, What’s in a name?
It’s been called many things over the years, Lucite, Lucor, Interleaving Powder, Interleavant Powder, Glass Separating Powder. No matter what you call it, TEK Interleaving Powder from Teknapack is manufactured to the highest standards and is backed by over 20 years of technical support and industry-leading customer service.
TEK Interleaving Powders for Float and Tempered Glass are available in both Adipic Acid and Boric Acid blend formulations.
TEK Interleaving Powders for soft coat glass are very uniform in size and also resilient to avoid damaging delicate multi-stack coatings.
TEK Interleaving Powder for hard coat glass is very uniform in size and is made from highly abrasion-resistant Ultra High Molecular Weight Polyethylene.
Since 1996 Teknapack has supported customers with industry-leading customer service and product development support to stay ahead of the demands of an ever-evolving industry.
To understand Interleaving powder a basic understanding of flat glass in necessary.
Since about 1960 the majority of flat glass used for architectural glazing and automotive windows has been produced by the float glass process: (Wikipedia article about Float Glass)
Float Glass is very flat on both surfaces and unlike earlier glass produced using the drawn sheet glass (Fourcault) process, Float Glass requires no surface polishing to achieve flat surfaces that are suitable to coating or laminating.
Float glass can be produced and packaged very quickly. Glass is packed in stacks, much like pages in a book.
Because float glass is so flat, when one piece of glass (often referred to as a Lite) is placed directly against the next Lite air is pressed out from between the Lites and the two pieces become “stuck” together. In reality, atmospheric pressure on either side of the two Lites of glass is pressing against the glass which makes it very difficult to separate the glass.
To deal with this unpacking problem some form of parting material is required. Many glass manufacturers used paper to separate Lites and this is still in use for special applications. Using a parting compound also called separating powder, Interleavant Powder or Interleaving Powder is a preferred approach because there are less cost and less handling involved and when the glass is unpacked, the powder is easier to clean up when compared to paper.
Interleaving Powder is applied to the glass to create a little air space in between. That air gap makes it possible to de-stack glass for fabrication.
Like many things in the world when one problem is solved and a new problem is created.
The air gap provided by the separating powder also opens the edges of a pack of glass up to the surrounding environment. Plus the air gap is filled with whatever air was floating around when the glass was packed. Often, the available air is high in water content.
Glass is tough stuff but it has a weakness for caustic chemicals. The technical name for common flat (float) glass is soda-lime glass. (Wikipedia article on Soda Lime Glass) Read the Wikipedia link if you want all the details.
Now, this is a simplified description of the chemistry involved but the short answer is that float glass has sodium in it and that sodium likes to get around.
Sodium likes to bond with hydrogen and oxygen which is what water is made of. So if two pieces of sodium-rich glass have a gap between them and that gap is filled with wet air, the sodium ions will be attracted to the hydrogen and oxygen in the air and faster than you can say chemistry a nasty corrosive chemical called sodium hydroxide is formed. Sodium hydroxide will etch the glass. Think of a drinking glass that’s been through the dishwasher 10,000 times and looks hazy, that is pretty much the same chemistry going on.
To prevent glass surface corrosion, which people in the glass industry also call “glass staining”, some sort of additional chemistry is needed to inhibit the formation of staining.
Glass industry scientists have been working on this problem for decades. The first obvious invention of modern Interleaving Powder is documented by US patent #2,992,747 which was granted to Florian Atkeson on July 18, 1961. Among a variety of claims, he describes using Calcined Borax for the stain inhibitor and Nylon Floc as the mechanical separator. In the years since that patent in 1961, over a dozen related patents for clever ways to separate glass and prevent glass staining have been issued and have become part of the public domain, making them part of the history of the glass industry.
A variety of companies have produced a spectrum of glass separating powders since the early ’60s, usually composed of Lucite beads and adipic acid. Sydeline Corporation was for many years the dominant player with its Lucor N powder, LA50 powder, and Lucite 47GS but others have stepped into the market over the years to offer options to the glass industry.
In 2020 Teknapack reentered the glass interleaving powder market after fulfilling a 5-year obligation to stay out of the market. Teknapack is working on new products to separate and protect whatever sorts of glass scientists will develop in the years to come.