Just a technical point. Acids don't "dilute" epoxy, they neutralize it
and prevent it from curing. That's why oak can be a problem. I prefer to
use polyurethane glue for bonding oak.

Acetone, lacquer thinner and denatured alcohol (among other things) can
be used to dilute (thin) epoxy and will not adversely affect the cure.
However, they can cause a reduction in strength if too much solvent is
used, as the amount of solids in the bond is reduced.



William R. Watt wrote:

epxoides can be diluted with acid before they set. you can clean your
hands and tools with lemon juice or vinegar. all oaks contain tannin
(tannic acid) which dilutes epoxy and makes the bond weaker. white oaks
(english and burr) are lower in tannin than red oaks. you can sometimes
eat the acorns from white oaks without boiling off (leaching out) the
acid, hence the common name of sweet oak. you will have less dilution with
white oak.