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tango

Yellow for ground

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Hi

Three years ago I made diluted turmeric in alcohol. Then filtered that and used the yellow alcohol to make shellac. Unlike the turmeric only diluted in alcohol without shellac that dissapeared soon. This resulted a nice yellow ground, the best yellow I made and lightfast. I saved a sample. It is not a "desired golden yellow"  but is the only acceptable yellow for ground I was able to make.
Because I seal the wood with oil varnish and plaster of Paris I was thinking about transfer the turmeric from alcohol to oil.

May be boiling the alcohol with the oil until the alcohol is evaporated completely ?
I know I can coat the wood after sealing with P of Paris with the yellowed shellac  but I refuse because , to achieve a nice color with oil varnish needs a lot of coats and I don´t whant add to much to the wood.
I am overthinking?

So, the question is:
Can I transfer turmeric powder in alcohol solution to linseed oil?

Thanks in advance
Regards
Tango

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I think that using a dry pigment is the best way to color oil varnish. Sometimes I use Terra di Siena naturale for that. 

Old books mention diluting something in alcohol and than incorporating it to the varnish, but I find it too complicated.

 

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You need a binary solvent to extract curcumin from ground turmeric. Alcohol + water in a ratio of 60/40 v/v is a popular choice in pharmaceutical experiments. Once you have the extract after about 48 hours of soaking, simply filter to get rid of solids and then evaporate the solvent by either slowly heating it or exposing it  to room temperature in a wide shallow tray. This will concentrate the curcumin and increase colour intensity.

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15 hours ago, tango said:

So, the question is:

Can I transfer turmeric powder in alcohol solution to linseed oil?

Thanks in advance
Regards
Tango

Perhaps, but I wouldn't count on that. Dyes and pigments can act differently, and have different degrees of color change over time in different varnish mediums.

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Tumeric is not that light fast, it can "seem" more lightfast when mixed into a film building finish,but will be prone to fading quite dramatically. I suggest using uv lamp exposure to mimic sun exposure over time. It will leave a  little color behind, but my extensive testing with Tumeric found that over time it fades to virtually no color at all if left exposed enough to the sun.

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Hi.

Sorry the long time from my first post. Finally I did not add shellac with turmeric. I used an uv box , made on last november, for darkening some.

I am happy with results.

Thanks all for advises.

Regards

Tango

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Madder in alcohol is a good ground color.

Beware! Most natural colors are very pH sensitive. A madder Yellow ground will turn PURPLE if applied over a strong base!

Always test on scraps before applying on your instrument.

Oded

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On 6/22/2020 at 10:35 AM, odedkishony said:

Madder in alcohol is a good ground color.

Beware! Most natural colors are very pH sensitive. A madder Yellow ground will turn PURPLE if applied over a strong base!

Always test on scraps before applying on your instrument.

Oded

Oded, are you back? did you loose your old login info? nice to see you...

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On 6/22/2020 at 1:35 PM, odedkishony said:

Madder in alcohol is a good ground color.

Beware! Most natural colors are very pH sensitive. A madder Yellow ground will turn PURPLE if applied over a strong base!

Always test on scraps before applying on your instrument.

Oded

Welcome back!!!  Very good to see you around.  :)

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