Why are cracks in agate filled? Cracks are filled for two reasons: first, to prevent breakouts from the cracks (stabilizing the material) and to obtain a closed surface, so that later when polishing, no polishing agent can penetrate the cracks. These polishing residues are then difficult to remove.
Which glues are suitable for filling?
Thin-bodied, transparent, low-yellowing adhesives are suitable for filling. For example, superglue, UV glue, or special thin-bodied resins.
UV glue and superglue have the advantage of curing quickly.
When should the crack be filled?
The crack should be filled after coarse grinding. If the crack were filled before coarse grinding, it could reopen during grinding.
It often happens that new cracks or cavities appear during grinding, in which case refilling can, of course, be done at any time.
Filling with Superglue
Filling with superglue is a simple and quick way to fill cracks. To do this, align the agate flat, apply the glue as thinly as possible but with the necessary amount over the crack. An activator can be used to speed up the curing process. Be careful to spray only a small amount. If the crack is too deep and the glue cures too quickly, this can cause the stone to crack. Important! It takes time for the adhesive to penetrate the crack, so apply the activator a little later. The stone can be ground after a few minutes.
Filling with UV Glue
You can also fill with UV glue. The process is similar to superglue, but curing is done with UV light. The stone can be ground after a few minutes.
Filling with Resin
A good option is to fill with thin-bodied resin. The advantage here is that the resin can penetrate deep into the crack due to the long curing time. However, handling is a bit more complex. The resin must be mixed correctly with the hardener, and curing takes a very long time. As a result, the stone cannot be ground immediately.
