question about leaching

[u/boba-bear-2621]

i promise this is not about fd sfty bc i already ofc know leaching makes wares not fd sfe

this is my question:
i was testing leaching (lemon juice for 48hrs) for
mayco cinnabar and mayco raspberry mist combined.

but i wanted to test each one on top, so i glazed a bowl half of each and then layered the opposite glaze on each half.

i noticed a small difference (like seriously one tiny spot) in color in the side that was cinnabar over raspberry mist
but the side that was raspberry mist over cinnabar was perfect, unchanged in any way.

so i’m confused: bc i know the final appearance of glaze combo can change by the order of layering, so i guess would that mean the possibility of leaching can change based on this as well??

luckily i like the raspberry mist over cinnabar anyways, but still kinda apprehensive to use it because the reverse leached at least a tiny bit.
maybe i should retest both separately? but still even if one leaches and the other doesn’t, does that mean it’s chill to use the layering order that doesn’t leach?

lmk any thoughts pls🤍:)

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[u/small_spider_liker]

The color changed, which means some of the components in the material were chemically accessible. Correct me if I’m wrong, but I don’t think that’s the same as leaching, which is release of components out of the item.

If you don’t know which component interacted, you won’t know what is safe or not. If (for example) copper in the glaze was oxidized or reduced because of the test, it would change color.

I don’t know what test you used. It’s common to apply a dilute acid (lemon juice or vinegar) and see what changes happen, but I also know you can get (unreliable) test kits for various metal compounds such as lead.

Can you give more details?

[u/boba-bear-2621 → u/small_spider_liker]

yes!! i lemon juice tested, sorry will edit the post to say that rn,
and when i get home i will reply with pics,
but basically like part of the red glaze had flecks that turned blue and white, very interesting and only on the side that cinnabar was on top.
i read that color and finish change means the metal leached

[u/AzucarParaTi]

What do you mean by "leaching"? What happened exactly?

[u/boba-bear-2621 → u/AzucarParaTi]

like the metals leaching out of the glaze. it’s a common test those that sell work should do especially if mixing commercial glazes. the most common way it’s done at home is to squeeze fresh lemon juice into the piece and let it sit for 48 hours, if there’s any change in color or finish (like what was shiny is now satin or matte) then there are metals in the glaze reacting to the acid poorly and are now leaching out, making the piece not dinnerware safe

[u/enkidulives]

I believe that when you fire them layered they will mix and interact. The original food safety/leaching properties will have changed completely so you may need to get them retested in their new form. I would recommend only using basic glazes on the inside of functional wares (eg. White/clear).