[Katherine Swift]

Jessica,

This is strange!

Are you sealing the images first?  I would definitely recommend that (seal with either clear packing tape or a clear drying glue) before including in the resin.

I will also send a tech support request to the company that we got polyester resin from to see if they can comment.

[Jessica]

Hello, I really need help. I cant find the answer to this anywhere.

Im casting with polyester resin in a little glass bottle and putting in a hand painted paper butterfly (painted with acrylic paint). As Im watching it cure it looks fine then a little while later the butterfly turns a bright shiny silver. It looks like I cut the butterfly out of tin foil.
 What the heck is going on??
Thank you

[Katherine Swift]

Jessica,

This is the comment from the manufacturers tech support team:

We?ve seen this weird phenomenon when casting fresh items like roses or insects: we believe it is from excess moisture in the embedded item. We?ve also seen it when the casting resin is too hot/ has too much catalyst. We would recommend that the paint be allowed to dry overnight and that the volume of catalyst be reduced by about 1 drop per ounce of resin.

[T]

This effect is called "silvering" and is caused by air between the embedded object and the resin.

The object must be dry and sealed before embedding in the resin. If the object isnt sealed, the air inside the object is released and clings to the object creating a thin layer of air around the object. Or uneven surfaces on an object trap the air and create this issue. If casting metals, the exothermic reaction of the resin can cause expansion of the metal, and as the cast cools, the metal contracts causing the air pocket.

I always seal any object with a clear coat and leave to dry for a couple of days to degas the finish applied. When Im ready to embed the object, I use a brush to coat the object with the clear catalyzed resin to eliminate air being trapped.

[Author]

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