Why are cracks in agate filled? Cracks are filled for two reasons: firstly, to prevent chipping from the cracks (to stabilize the material), and secondly, to create a closed surface so that polishing agents do not penetrate the cracks during later polishing. These polishing residues are then difficult to remove.
Which glues are suitable for filling?
Thin, transparent, low-yellowing adhesives are suitable for filling. For example, superglue, UV glue, or special low-viscosity 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 voids appear during grinding; in such cases, 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, level the agate and apply the glue as thinly as possible, but in 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, it 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 filling with low-viscosity resin. The advantage here is that the resin can penetrate deep into the crack due to the long curing time. However, handling is somewhat more complex. The resin must be correctly mixed with the hardener, and curing takes a very long time. This means the stone cannot be ground immediately.
