The pH of glue varies greatly depending on the type of glue. There's no single answer.
Types of Glue and Their pH
-
Hide Glue: This type of glue typically has a fairly neutral pH, ranging from 6.5 to 7.4. However, variations are possible.
-
Bone Glue: In contrast to hide glue, bone glue tends to be acidic, with a pH generally between 5.8 and 6.3.
-
Polyvinyl Acetate (PVA) Glue: Many PVA glues are designed to be pH neutral or acid-free for archival purposes. These are frequently marketed as "neutral pH adhesive" and are commonly used in bookbinding and conservation. However, the exact pH can vary depending on the manufacturer and specific formulation. Adjusting the pH of PVA glue might be possible through the addition of substances like sodium acetate to act as a buffer, as discussed in some online forums.
-
Hot Melt Glues: These glues are often cited as a source of failure in applications like bookbinding due to their rigidity. Their pH is not consistently documented but may not be considered neutral.
-
EVA (Ethylene Vinyl Acetate) Glue: Some EVA glues are specifically formulated to be neutral pH adhesives.
Importance of pH in Glue Applications
The pH of glue can be crucial in certain applications. For instance, in bookbinding and archival work, acid-free (neutral pH) glues are preferred to prevent damage to materials over time. Acidic glues can cause degradation and embrittlement.
Finding the pH of a Specific Glue
To determine the exact pH of a specific glue, you would need to use a pH meter or test strips. The manufacturer's specifications might also provide this information, particularly for archival-quality glues.