Van Dyk Crystals?

[Asquared]

I'm trying to re-finish an antique table top. The wood is straight medium grained - I'm guessing mahogany. It looks like it was french polished and had very even medium-dark brown colour. When I sanded it back the wood is not evenly coloured. It varies from light to dark brown across the boards.

A chap in a wood work shop said it was probably done with VanDyk crystals. He thought they may have been mixed in with the finish so that the colour was in the finish rather than the wood being stained.

Can someone enlighten me about VanDyk Crystals. What are they, how are they used? Are they the same as or different to Condies Crystals? Is this likely to be the answer to how it was finished or is there a better way to get that even coloured finish?

Appreciate any feedback.

Andrew

[Pete]

Andrew,
I found Van Dyke crystals on the net. Try www.garretwade.com or http://www.woodfinishsupply.com/LIBStarCatalog2000.pdf

I still cannot figure our what they are!
I can say with some certainty that they are not Condy's crystals (potassium permanganate) I think they are derived from walnuts(?). Not much information out there on the net.

Hope this helps a little.
Peter

[This message has been edited by Pete (edited 18 September 2001).]

[Iain]

I've got a copy of an old woodfinishing book circa 1850 and I am sure these are referred to. I have not responded because I can't find the damned thing. I will continue looking......

[ubeaut]

Been hanging back to see if anyone ever actually read my book. I know that many BB members have a copy. Oh well.........

From: "A Polishers Handbook" by Neil J Ellis

VANDYKE CRYSTALS - Dissolved in hot water give rich brown shades to a wide range of hard and softwoods. By adding ammonia mahogany will turn a rich warm shade and on Oak it produces a greenish brown tone. Add potassium bichromate and it will produce a dark reddish brown in these two timbers.

These are a non toxic brown crystal or powder. Bloody near impossible to find in Australia. Last lot I had was imported from France. Don't have any left.

They are and water soluable. So don't try putting them into your polish. More than likely the top would have originally been dyed using Potassium Bichromate mixed in water. This was a very common dye for mahogany and many other tannin rich timbers.

You will not be able to use either of these on the table now unless you strip and sand the whole thing back to raw timber and if you do that you probably need shooting.

Hope this helps.

Cheers - Neil

[Shane Watson]

sand the whole thing back to raw timber and if you do that you probably need shooting.

Ya better load ya rifle then Neil



[This message has been edited by Shane Watson (edited 18 September 2001).]

[Pete]

"dissolve in hot water....." So what are they? From what I can find, it seems that they are some sort of aqueous extract from Walnut (shells?). Maybe some containing a tannin or something. The fact that the go brown with Potassium bichromate (nasty stuff with lots of chrome 6+) suggests that they are easily oxidiseable, again pointing to something organic.

Put me out of my misery pleeeeeze!
Cheers,
Pete

[ubeaut]

Pete - It isn't the crystals that turn brown with the addition of potassium bichromate it is the timbers - (mahogany & Oak).

VANDYKE CRYSTALS - Dissolved in hot water give rich brown shades to a wide range of hard and softwoods. By adding ammonia mahogany will turn a rich warm shade and on Oak it produces a greenish brown tone. Add potassium bichromate and it will produce a dark reddish brown in THESE TWO TIMBERS.

Strewth when you ask for an answer at least read the reply properly.

It seems pretty superfluous what they are made from as you more than likely won't get them in Australia anyway. However if you really must know here 'tis:
Vandyke Crystals are made by an ammonia extraction process from Vandyke Brown (a naturel earth containing organic matter)

Hope this finally puts you out of your misery.

By the way. The extract from Walnut is called (Walnut Crystals or Cassels Extract) also pretty well unobtainable in Australia. This is a modern day version of the old Walnut brew (brou de niox) which you can make yourself if you have a heap of dried outer skins of walnuts and a lot of time to cook them (3 days continuous, in a brew) The recipe is in my book.

Cheers - Neil

[Marty Lott]

Hi guys, I use Van Dyk Crystals regularly, it gives cedar a rich warm colour, perfect for matching new cedar to old. I get it from S.A & S.Stimsons. Graeme Brown Antiques also stocks it. If you need the full details I'll look it up on Monday.

Cheers

[Asquared]

Neil

I've got your book and I did read that reference first but I was looking for more information. It seemed from what you said that they wouldn't be something you mix with shellac. You've confirmed that. This being the case I was wondering if I'd get some advice on how I might approach the task. Thanks for the advice you've all given.

You are probably right too that I should also be shot - I did sand the thing back to bare wood which is why I knew it was not of consistent colour when the finish was removed. Unfortunately the reason I had to sand it was because the top was made from three separate triangular pieces which had all come apart as the wood shrunk with age. When I reglued it, despite great care and effort, the three pieces did not sit perfectly flush. The new joints would always stand out even if I had got them flush. So, I decided to sand it back and flush the joints.

Thanks again for all your advice everyone, I appreciate it.

Andrew