Dyeing Agates

Dyeing of Agates Explained Here!

We will explain to you the process of dyeing agates, how to prepare them and how to dye them, with chemicals and tints.

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Dyeing Agates

To start, the word agate will be used interchangeably with the word “chalcedony”, as they are the same thing.  A suggestion is to place a piece of material to be dyed into a solution of Potassium Chromate
overnight.  If the stone is yellow in the morning, dyeing will be easy to accomplish.

Processing

First, ensure that the material has been cleaned, to remove any debris, and of course, best, to have already slabbed, cabbed, or polished the stone to be dyed.  The oils must be removed from the stone entirely, which can be done as such.  Bring to boil the agate in a strong solution of water and sodium carbonate.
Allow this to cool and remove the agate and place in a pot of clean water and heat to a near boil, then cool, which should remove the traces of sodium carbonate.    Then, place the agate into cool concentrated nitric acid,
which will remove any iron compounds.  Heat this material for 24-48 hours, bring to a near boil for several hours at the very end of the cycle, then after cooling, wash and heat to a boil the agate in a clean water bath three or four times, at which point you will have the most professionally prepared agate ready for dyeing.

How to Dye Agates Red

To dye agates red, the solution is as follows.

Place 1/4 pound of iron filings
into 1 lb of concentrated nitric acid.  The resulting fumes are going to be a corrosive, poisonous brown fume, so this mixture must be done outside or under a lab hood.  This stuff will bubble and heat up, allow to cool for 24 hours, then decant the clear liquid into another container.  This is iron nitrate, the liquid needed for the next step.

Place the cleaned, prepared slabs into the liquid iron nitrate produced from the last step and allow to soak for between 1 to 4 weeks, depending on thickness.  1/8′ needs a week, 1/4″ needs 3 weeks and 3/8″ needs 4 weeks to dye.  Remove the agate, wipe them dry and place into an oven to gradually heat.  Bring the material up to 365 degrees and heat for 3-5 hours.  At this point, it is time to soak the agates in the iron nitrate for an equal amount of time, repeating the drying step after soaking, but for a lot longer, 2-8 days, depending on thickness.  This long drying is needed, in a roasting pan
, as the final step is to raise the stones to 450 degrees and the long drying is needed to make sure the stones do not explode when the stones are brought up to that temperature   Allow to cool, then, remove from the roasting pan
 You should have a deep red colored agate.  Note, while lab grade iron nitrate is available, the professional lapidary artisians claim it does not produce the same results.

How to Dye Agates Black

Dissolve 375 grams of sugar into a liter of water, producing a thick liquid similar to honey.  Soak the slabs in this solution, heated to slightly above room temperature for 2-3 weeks, adding water to the solution as it is lost from evaporation. Rinse the slabs off and place into a bath of concentrated sulphuric acid
, which you will then warm slowly over an hour until the solution finally reaching 635° F for an hour.  Allow the solution to cool, then remove the agate and wash, repeating the process to remove the acid.  Soak the slabs in a solution of sodium bicarbonate to neutralize the leftover acid.

How to Dye Agates Blue

Bright blue agates are very desirable, below you can find the recipe for making this material.

Dissolve 250 grams of potassium ferricyanide
into 1 liter of lukewarm water.  Place agate into this solution, kept at a lukewarm temperature, for 1 to 2 weeks.  After soaking, wash the slabs and place into a solution of lukewarm ferrous sulphate
for 10 days.  This solution will cause the compounds within the stones to react and form the bright blue color that people known and recognize.

How to Dye Agates Green

Take 620 grams of chromium trioxide
in 1 liter of water and place agates into the solution for 2 weeks, or longer if material is thick.  Remove the material, rinse and place in a sealed container with ammonium carbonate,
to sit for 2 weeks.  After this time remove the slabs from that container, place into a roasting pan
and place in an oven to “fire” the agate, bringing the oven up to 500 degrees for a few hours.

How to Dye Agates Yellow

Soak the agate in a concentrated solution of Potassium Chromate,
then wash and dry, which should give you a nice yellow tone.

And with this, our limits of dyeing knowledge are capped.  All of these procedures should be done under a lab hood or outside. MSDS sheets should be reviewed before working with any chemicals and proper lab equipment, including safety glasses, gloves and proper eye wash stations, anti-acid creams and clean up kits available.

 

Slab showing dyed colors

All Five colors, plus natural end caps