Saturday, May 12, 2018

Decorating a full Greenwich garniture: Part 3: Still things to learn.

So, by a fortunate series of work related events, I found myself needing to go to South Africa, by way of London. This would mean, with an added lay over, I could visit the Wallace museum in London, where the original armour resides. It would also be nice to visit with Dr. Tobias Capwell, the armour curator at the Wallace. 
Dr. Capwell was gracious enough to take time out of his Monday morning to open up the A62 case and allow me to compare my etching samples to the original. While I was excited by this fortuitous opportunity, putting  your work up next to the original can be scary, since no matter how close you think you are, a side by side comparison will almost always reveal differences instantly. (some times major ones)
This was the case with my etching samples. While my armour is considerably larger than the original, and as a result I have had to enlarge the decorative pattern, I was not prepared to see such a huge difference in dot size.
The original Greenwich armour was considered a moderate decoration option when it was made in 1585. I have learned from Dr. Capwell, there are 4 or 5 known surviving (incomplete and complete) examples with this same etched design.
 The example in the Wallace, which I have been using as my main reference, has dots that are about half the size of the ones I have done. Being half the size, there are also about twice as many.
 The main part of the etched design seem to be pretty close between mine and the original, especially when you take into account my suit is so much larger. But, I will have to experiment with application and etching of these new smaller dots, since the resist can come loose after a number of paste applications.
It was not possible to open the front of the display case, only the shallow side sections, so some of the pictures had to be taken at odd angles or through the glass of the case, but they are still very useful in showing the differences.

Here is the Left lower leg, next to the original. It is a little deceiving because my ungilded piece has more contrast in the etched areas, but I'm pretty happy with the general pattern. It is also clear to see how much bigger my armour is. Now the average height at the time was maybe 5'8" and today it's 5'9" to 5'10", but at 6'3" I'm still tall for today, so my leg armour looks giant next to this one, made for a fellow 5'6". (Yes, they are side by side)
This is the exact reason I started with the greaves, because, while I thought I had a good idea on what needed to be done, I figured if there was any adjustments to be made, better to figure it out before I got to the upper part of the armour. 

The is one of my earlier test pieces next to the decoration on the reinforce breastplate. Being an early test, I didn't worry about lost dots in the pattern, but here you can clearly see my dots are much too large and not nearly dense enough, even given the scaled up main pattern. Also, this being the larger part of the pattern on the original breastplate, the floral work inside the figure eight is denser than my sample, which is a copy of the greave pattern, which has smaller floral work.
My sample also has the two different boarder vine patterns. Clearly the right side one is closer to the original armour.
The plan , if I can produce the smaller dots consistently, is to gradually make them smaller and denser as I work up the armour. So that the upper part of the suit is closer to the original. Given the over all enlargement of the design, I probably won't go exactly as small as the original, but I will try for something much closer than I am now.

I have not been satisfied with the overall depth of my etched pieces. While some pieces seem pretty good, others are not. Consistency seems be elusive. Longer etch times seem to damage the vinyl resist, partially due to the metallic copper deposits and this causes the paste gets underneath and degrades the original surface. Mac's research into etching pastes has recipes which include charcoal. We have suspected this may have some type of conveyor like effect, either to bring the active etching ingredients to the surface of the steel, or remove copper. Before my trip, I ordered some to experiment with. I received both "activated" charcoal powder and the Cowboy charcoal Mac referenced. The limited test I have done do not show any clear advantage of one over the other. They both seem to reduce the metallic copper deposits on the steel surface when the etch paste is removed. This makes surface cleaning between etchings much easier and less destructive to the resists. (My ratio was 4 prts. CS / 2 prts salt / 1 prt charcoal powder)
My brother, who does a lot with 19th century guns, mentioned bone charcoal as being very desirable for case hardening. A little research on bone charcoal revealed some research done in using this type of charcoal to absorb copper contamination in water and found it to be very effective. I ordered some and will test it this week to see if it improves the copper absorption from the steel surface.

The other issue I wanted to address is the size of the dots on my samples. Since my trip to the Wallace showed my background dots where considerably larger than the original. I had spent the long 10 flight back to LA pouring over my reference pictures again and comparing those to what I had just shot with my example next to the A62. I was also going over in my mind what I needed to change, as far a technique, in order to apply the tiny dots.
Using the "hena" plastic bottle to apply the dots smaller turns out to be quite easy and in fact, I have gone the other way and the dots now may be too small, given that the pattern for my armour has been enlarged to account for the armour being bigger. 
Here are tests with smaller dots:
While the overall size is a pretty good match, I'm not sure the smaller dots work as well, so I'll probably split the difference.
The other thing I'm not happy with is the gold. It is not nearly deep enough in color. As you can see by the above photograph, (more apparent in the side by side images in my earlier post) the original has a much yellower gold, a result of the much heavier gold deposit using the fire gilding process.
In this sample, I used a torch to blue the edges and as a result the gold was slightly discolored. I may be able to use this to my advantage, given that the salt bluing, with its more controlled temperature gave the gold an even orange hue. With a reapplication of gold, this color was corrected while still retaining a little of its darker color.

This latest sample has very good depth. A result of 5 paste applications at 1 hour each and a 6th application at 12 hours. With the charcoal added to the paste, the vinyl was less effected by the copper deposits. I also brushed some of the asphaltum resist over the entire surface and cleaned it off with solvent. My hope was this would leave trace amounts in the corners where the vinyl met the steel, hopefully "sealing" the vinyl to the steel a little more effectively. The combination of this and the carbon defiantly improved the vinyls ability to survive repeated cleanings. The last 12 hour etch did get under both the vinyl and the asphaltum dots, so it may not need to be left as long. Perhaps 6 hours will be better.
I have the artwork and vinyls cut for the right greave and will get those applied this week and should have the second greave completed in the next few days. Then on to the cuisses.
I've done some more tests and it seems the bone charcoal is pulling more of the copper away from the surface, or at any rate, it makes cleaning the copper deposit off the steel much easier between etches. It also seems to allow for longer etch times with greater affect. The bone charcoal I have has a slightly larger grain than table salt.
I've completed the right greave front plates and used the bone charcoal mix for 3 hours and it seemed to etch effectively.
My ratio for these tests was 4 parts (By volume) Copper Sulfate - 2 parts salt - 1 part bone charcoal -1 part 15% vinegar. I put the powdered components in a bucket with the snap on lid, then shake to mix thoroughly. Then add the vinegar and shake again. Let sit for 1 to 2 hours, shake vigorously again. 12 to 24 hours later, the paste is like guacamole. With the charcoal, age does not seem to effect the paste's etching rate noticeably.
I have made some tests with smaller, more consistent dots and these are looking much better. Although, I now see I have the dots too dense.
Bluing: The study that was done of the Buckhurst's color, concluding it was steel exposed to atmosphere at 250 c, this temp does not seem to work, with the technique I'm using. In the salt, at 250 c (482 f) the color was very pale straw, barely perceivable. It wasn't until 300 c or 580 f that it shifted to blue. I got an amazing color and the pen plated gold got a little yellower, not as orange as the previous test at 650 f. The photo doesn't show the gold as well as it looks in person, but, it's still "weak". Mac has pointed out that over time (unknown duration hours or weeks) the blue color may be achieved at the 250 c temp. But in the salt, the color was reached in a minute or so at this higher temp and seemed controllable. Of course, this mean a very big container of 500 degree salt for the breastplate and such. The heat treat company may have a tank with a material I can use, if they are willing.
There is a little bit of spotting, which I believe was surface contamination. The surface is also sensitive to finger prints, even with two coats of paste wax.

The test here was pen plated with 24k gold and I was not thinking and forgot to wire brush, per Mac's advice, the etched areas before plating, resulting in the background areas being a bit gray. The pen plating is still paler than the real armour, but, it does shift a bit in color with the bluing, and gets a touch richer yellow, which is desirable. I'm still on the fence about fire gilding.
Since the real armour shows no signs of gold on the background dots, this means they were either blue, like the rest of the bare steel, or had been cleaned off to be silver. After gilding, I cleaned off an area of dots, in the upper left and let the dots turn blue. The effect in my opinion was a bit drab looking, so, rather hastily, I sanded the blue off to see the effect. I think I like the silver dots.
I finished etching the right greave. While I'm happy with the improvements in artwork and scale of the design elements, I'm still not completely happy with the consistency of the etching, nor the ultimate depth I'm getting. There is some variables I have been unable to pin down.
Here is a good look at the progression I've made with the quality and neatness of the artwork and the gold plating. (Old to new - left to right)

To address the etch depth and consistency, I thought I would do a formula test.
 I made three different formulas of etch paste (by weight):
#1- 20 grams of Copper Sulfate / 60 g of salt
#2- 40g C.S / 40g salt
#3- 60g C.S. / 20g salt 
Then after thoroughly mixing the two powders together, I split these into two sets. To one set I added 15g of bone charcoal to the 2nd set I added 30g of bone charcoal. The 30g set I labeled "A" (1A, 2A, 3A)
To these 6 batches I added 15g on 15% vinegar and mixed.
I had final mixtures of:
#1- 10 g C.S. / 30 g S. / 15g B.C. / 15g V.
#2- 20g C.S / 20g S. / 15g B.C. / 15g V.
#3- 30g C.S. / 10g S. / 15g B.C. / 15g V.
#1A- 10 g C.S. / 30 g S. / 30g B.C. / 15g V.
#2A- 20g C.S / 20g S. / 30g B.C. / 15g V.
#3A- 30g C.S. / 10g S. / 30g B.C. / 15g V.

After 2 hours I remixed and let them sit for 12 hours. I then remixed them a final time and applied them to the test plate.
As the bone charcoal has consistently reduced the metallic copper deposited on the surface of the steel, I decided I would do this test as long duration etches. (verses 1 hour, then clean, repeat).
The first was 7 hours & 20 minutes. I cleaned off the paste and noted the damage to the resist (vinyl & asphaltum resist)
I used an older vinyl resist sheet (orange) that had some dots on it, so I left these and just added asphaltum dots to some of the surrounding area. 
I then did a second etch for 16.5 hours. This time all of the resist, both vinyl and asphaltum was failing. I cleaned the surface and gave a lite sand to the high points with 600 grit paper. While the etch depth was good, the results were frustrating, as I did not see very much difference in the etch depth, which I was expecting given the wide range of ratios I had used.
I cut the piece in half to see if I could better see a difference in etch depth, but not really. The only noticeable thing was background coarseness, due to the large quantity of bone charcoal which is coarser than the other ingredients and of course does not dissolve in vinegar.

I'm going to do another test with the same C.S / salt ratio, but this time use different charcoal, wood and powdered Also 10g of bone charcoal, 5g and 0 bone charcoal.
 I have tried wood based charcoal and it did not seem as effective as the bone charcoal. I only tried the bone charcoal after my brother mentioned it was prized for it properties when case hardening gun parts in the 19th century. When I did some research, I found where it had been used to absorb excess copper from contaminated water and was very effective. Now, I only did one or two tests with the other charcoal, and in minor amounts. This recent test was to see if a larger percentage of the charcoal effected the aggressiveness of the etch. Until I do some other tests, I feel this question is still unanswered.

EDIT-Current formula (as of July 2021) After over 100 tests and 99% of the armour complete, the formula I'm using now with satisfactory results is:
100g fine salt (Salt flour)
100g Copper sulfate fine crystals
25g Bone charcoal
13g activated wood charcoal
Distilled water to make it a thick paste.
The reaction with the salt, will cause the material to freeze, so after mixing, you need to let the paste sit for and hour or so, and then t\remix it. NOTE: Do not make your initial mixture too wet, as after you remix it, the salt gives up some water, and the paste gets wetter.
If it is too runny, you can add charcoal to thicken. I have found 3 or 4 90 minute etches (fresh paste for each) gives you considerable depth, equivalent to late 16th C armour.

Next: The Ah Ha Moment!

No comments:

Post a Comment