Epoxy for the Mercury Fuming Box?

[Pollywog]

I am about to see a machinist next week in order to fabricate the mercury box.

I know that using stainless steel, which I will use fully, will prevent much of the mercury from attacking the material.

I know that epoxy coating on stainless steel would be required to protect the surface more, would any regular epoxy for stainless steel be required?

Such as the one here at http://www.steel-it.com/epoxy.htm

I’ve done powder coating on stainless steel before, but I don’t think that this form of application is suitable.

Any advise would be appreciated.

-Pollywog

[petecarney]

Why use stainless?

Industrial mercury containers are mild steel because iron is the one common metal which won’t amalgamate with mercury while stainless steel pipes carrying mercury contaminated natural gas have suffered corrosion due to chromium being leached.

In short I see nothing wrong with powder coated or epoxy coated mild steel.

-petecarney

[Pollywog]

Thank you for the reply Pete.

I had asked Mike Robinson on the material that he used for his mercury fuming box. He mentioned that he used stainless steel coated with epoxy.

Assuming that it’s probably similar stainless steel used for marine boats (316 if I am not mistaken), I thought of utilising the same material.

Interesting point on the possibility of mercury could amalgamate with this material. I thought this type is quite a stubborn material, hard to corrode in most conditions.

Perhaps Mike could explain on the choice of material? I wouldn’t want to build something that might risk leeching out the mercury fume.

[Mike Robinson]

A slight miss-quote here. The upside down pyramid body of my mercury pots are welded mild steel with a West System epoxy coating in the interior. All corners and inside angles are smoothed with epoxy filler to radius the seams. This allows for easy wiping down of the Hg condensate that forms inside. The outside finish is a decorative hammer finish paint. The stainless steel components are the threaded mercury cup, post for height adjustment, and two dark slides. My first Hg pot is also mild steel with a stainless Hg cup. I used gloss black high heat engine paint over autobody filler to finish the inside on my first Hg pot and that works well.

Mike Robinson

[Pollywog]

Thank you Mike for the overview.

I’ll do the adjustments on the materials as you had advised. I am relieved as the materials of choice for making it are getting cheaper!

[CasedImage]

This year I have been working on developing a design for a mercury pot to be made available commercially, which I will be launching in the ImageObject.com online store quite soon. The design is based around the C19th model of the inverted pyramid, which offers best surface for the condensing mercury to drain back down into the reservoir.
I have had a inverted pyramid mercury pot (alcohol lamp heated) since 2008 and have found no difficulty in removing the mercury for filtering or storage and question the need for a removable mercury cup. I believe there is an issue with these with the threaded seal where mercury can gain egress which is an unnecessary risk. A straight out inverted pyramid provides a unrestricted flow for the mercury to flow back down to the reservoir which the interface of a circular removable cup and inverted pyramid inhibits.  With the single piece dark slide assembly removed I’ve alwsy found it quite easy to pour the mercury out into a smaller vessel for filtering or storage.

The pots I have had made are stainless steel with a black heat resistant paint on the interior, which allows easy detection of where mercury droplets are present in the pot (had this on the 2008 pot from Jerry Spagnoli’s practice). The metal to avoid in mercury pot construction is of course aluminium, as mercury can dissolve it.

The pots I have made so far this year have had a static frame to give no movement in the pot (see attached image). I found with my 2008 model which was on a single post, that it could bounce a little and great care was needed to prevent this and mercury droplet bouncing up to hit the plate.
The current batch of 4 pots I am having made by my engineer varies this design with a telescoping of the legs to two fixed height settings (see google sketch up of the basic design). The shorter height is for use with the removable electronic heat elements which are controlled by a stand alone controller box (the previous design had the controller attached to the pot frame. The taller height is for when the pot is heated by alcohol lamp, in the absence of access to mains power.

The max format size of the pot is 8×10, I favour whole plate as a max size for daguerreotypes due to the reflection properties of larger plates but aimed for 8×10 as it allows for the developing of two half plates simultaneously , which is a difficult logistic if the max aperture is whole plate.  The facility to prepare, shoot and develop 2 plates at a time seemed a significant economy of operation to aim for. Attached is an image of the format reduction frames for the pot.

Differing from my 2008 smaller pot this one with a larger amount of steel displaces the heat more and moving beyond alcohol lamp heating has taken some testing, trial and error to achieve the right formula of apparatus to deliver a consistently and stably heated pot.  Attaining the right sort of heating element and digital controller for your design of mercury pot can be difficult.

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[Pollywog]

Fantastic and beautifully design setup Alan!

I will take in the advise on the material constructions and the most important part would be the interior coating of black heat resistant paint, which I assume the auto-shops / car body shops could provide the spray job on it.

[bunyaminergen]

To paint ; oven paint(Electrostatics Painting) can be used.

[Pobboravsky]

Alan,

Congratulations on the design and fabrication of the mercury developing boxes.  They are beautiful!   Have you arrived at a price in US$?  Please consider a  mercury-tight container to safely store the mercurizer when not in use.   Irv

[CasedImage]

Hi Irv, yes I’ve always used a thickly sealed container for my Third plate pot and when designing this one I could see another advantage in not having a single post suspending the pot – the footprint is uniform to the height and minimal to the maximum format of the pot. Still searching for the plastic container thats closest to the size though.
The costs have gone up and up on the pot from what I had been aiming for and I am awaiting the final engineering bill for the batch of four of the upgraded design so there is no surprises in the costs for each unit.

www.CasedImage.com

[Pobboravsky]

Alan, it is a great challenge to design a low-cost Hg’er. The 19th-century cast-iron, inverted, hollow pyramid design does this brilliantly and compactly. I store my 5×7 Hg’er in a surplus 50-caliber ammo box (bought on the web).(My hg’er is not cast iron.) There is a need for a “Starving-Artist” version of a half-plate size unit. Without any change in design the same unit could be bought either w/ or w/o a temperature controller. The thermometer or the thermocouple need not have its end sitting in the Hg. It could just as well be situated in a hole drilled in the cast iron – even close to the top of the unit. Just some thoughts. Irv

[CasedImage]

Actually the 1mm thick tube that the temperature sensor sits in, is sealed on the end that is inside the pot. That is to say there is only one opening in the pot and that is the top where the plate is placed. That is covered by a closed cell foam gasket and then the one piece dark slide assembly. It is actually three pieces of hdpe cnc machined for the 1mm thick stainless steel dark slides and the 8×10 plate seat. It is bolted together and with silicone sealant at the borders, the dark slides have stops on them to prevent them being fully withdrawn. I am adding walls to the sides to prevent air rushing around the heating area as I have found the fume hood makes it cool like a air cooled engine. Also I’m lagging the inverted pyramid above the heating element area to help the temperature stabilise quicker.

My intention to offer a low cost pot has been thwarted by the cost of mechanical and heat engineering, the first pots I have made and sold have actually costed at least as much to make as I sold them. That has been a research and development cost to the project though – the redoing of things till the formula is right. With the electrical heat engineering the cost has doubled from where I started to the final design I am using in the next 4 pots. In that the heat controller box is separate from the pot and the heat elements removable. To offer a low cost version I will sell just the pot with a alcohol lamp and a battery powered polder temperature thermometer and since the pot will have the mounts for the electric heat assembly, the latter can always be purchased later on.
When the full version is to be heated by alcohol lamp in the absence of electricity the temperature sensor for the electric heat setup has to be removed and replaced with the sensor probe of a battery powered polder, to monitor the mercury temperature.
I do want to offer a smaller version – up to 4×5″ in plate format but this will depend on how much less of a cost the engineer sees in the size difference (yes some less material but otherwise its the same amount of work), but fingers crossed.

www.CasedImage.com

[Pobboravsky]

Alan, I apologize for not making myself clear. I am not questioning whether your Hg’er is beautifully designed and fabricated — however it is out of reach financially by most people who would like to buy a unit. It may very well be that a PROFITABLE “starving artist” Hg’er may not be achievable. But that is where the challenge lies. [During your time in the US you likely heard Garrison Keillor’s monologues on The Prairie Home Companion radio program. You may remember the 93 year old Senator B. Thorvaldsen, one of the fascinating characters that lived in Lake Wobegon. Senator is his first name. He was at a gathering and in conversation with someone who said: Senator, what you need is a good woman. His reply was: I don’t care about good anymore. Your present Hg’er is more than — good.] What I’m suggesting is the equivalent of a Ford Model T that is affordable and meets the need – does the job. Irv

[CasedImage]

Hi Irv, no not assuming your questioning the design at all, I’m just detailing the design in my thinking aloud mode (I seem to be thinking about the mercury pots day and night) as am keen to explain whats going into it.

Affordable is a relative term, this is a custom made item with scarce availability, in a small market and given its coverage of all the main formats it is a once in a lifetime purchase. Spread the cost over even a few years and I think it represents a good investment. Being so robust with a small amount of easily replaceable parts it will have excellent resale as well. There is much equipment needed for this process and some might spend more on a large format camera and lens. With other equipment alternative low cost options can be achieved but with a mercury pot I think there are only safe and unsafe options. The alcohol lamp heated version will be much cheaper and hopefully a 4×5″ version will be even cheaper still.

Through facebook I hear from a lot of artists in the wider alternative photography genre who are looking to take up the daguerreotype. With the ImageObject event we aim to give daguerreotypists a conduit to the photo art market and get more artists making daguerreotypes. This mercury pot project hopefully will help with the latter and artists participating in the ImageObject event and also selling their artworks through the online store have an opportunity to recoup on their investment.

best
A.

www.CasedImage.com

[Pollywog]

I do agree with Alan as I began to see that making mercury pot (or any other equipments) in small batch or continuous run is an arduous undertaking, even more taxing on time and the expense. In my case, when I started to source for gears last year, most aren’t available at the time at, and in most companies that might be able to make them (the bespoke/custom) will charge quite high price, that turns most budget cautious practitioners away.

For me, though the handling dangerous chemicals is quite apparent with daguerreotype,the beauty is still too attractive to turn away from. I began to see then where I suppose every senior members here was sourcing out for the apparatus with something that is hardly known to many woodworkers/metal-smiths, and they priced to make them at high rate like making a custom cars. Which at the time, the community to give advise was even smaller than today. I respect the rigour you all had put into fining your craft. And I do see the logistic of the price that Alan had to come up to.

Though I do agree with Irving on where we wish for the day when the spread of this craft goes another mile where the equipments are available in reachable economy (with safety in the apparatus taken care of). I suppose when the demand of new-practitioners (like myself) reached to the suitable investments made by the apparatus-makers (funny, I am on this side as well), then the price may be made lower.

Until the day comes, I still have to go around and make my own apparatus and negotiate the prices and the logistics. This made me love my dag-making gears even more, despite the flaws and so many versions of what-not-to-do gears in the chipper. Though, I am lucky this community is here to guide and to give in their thoughts, which makes the needed difference from making major mistakes.

Now I have to go and bash those stainless steel into a pyramid.

I thank all senior members here who had chipped in and I will post the gears on the forum once it is done. Hopefully not too gaudy, and able to deliver the Hg fumes as it should once I powder coat the internal surface.

[jgmotamedi]

Just curious Alan, how do you remove the mercury from your pot? A pipette? Can you pour the mercury out from the top? The pictures look great.

[CasedImage]

Hi Jason
Same as my current pot, I remove the darkslide assembly and just pour it out into my mercury container. I’ve done this since 2008 with my other pot for filtering the mercury and never found it a problem, in fact I’ve always wondered why other designs bother with a removable mercury cup. Tipping the inverted pyramid slowly the mercury flows the joint of two sides of the pot and into the small PTFE container I use to store the mercury.

www.CasedImage.com

[Andy Stockton]

I also have a fixed base pot, but unlike Alan’s the darkslide setup on mine prevents pouring out the mercury. I use a 5ml syringe that I got from an online veterinary supply to transfer my mercury. I ground off the tip of the needle so it is blunt. I find that it gives me the most control when I move mercury in general and precludes any splashing. The thin needle lets me vacuum up even very tiny droplets. I store the syringe and the mercury in separate glass containers with metal lids. Glass/metal has proved to be the best combination I have tested for containing the mercury fumes. I store everything outside in a ventilated cabinet.

[petecarney]

Absolutely beautiful. I’d be interested to know what difference in temperature readings can be observed between having the temperature probe in the tube as described or simply strapping it onto the exterior wall of the mercury pool.

[CasedImage]

Hi Pete, I don’t have a temperature probe specifically designed to read surface temperatures, so may not be able to answer that. The tube that goes into the pot, for the temp probe to go into, has a 1mm thick wall, the pot itself is made of 2mm stainless steel. I would think that a probe just strapped to the outside of the pot will be effected by the outside environment of the pot and given its for working in a fume hood, it may effect the reading.

www.CasedImage.com

[jgmotamedi]

Thanks for the reply Alan, I guess we will be using one of these for the CAP workshops in November, so I will check in with you later off forum about use. I would also be interested in purchasing, when the time comes.

Sorry to have hijacked the thread Pollywog.

[CasedImage]

Hi Jason
Yes I currently have CAP’s pot back with me to have the static stand replaced by the new design plus some other refinements since I sold them it back in March. What you will be using in November will be the final design so all who pass through CAP’s doors can see the design in person, effectively being my agent in NYC.
Once I have some product photography on the new design I will start a new thread, my apologies too Pollywog.

www.CasedImage.com

[Pollywog]

Not a problem guys,

Sometimes silly questions sparks new knowledge (for me in this case) and news from others.

I am happy to hear the forum comes alive and hopeful it will always be.

I suppose for petecarney’s inquiry on reading the the surface temperature, one might be able to use the IR thermometer to have external reading. Though it might not be the actual temperature of what is going on on the inside the pot.

Keep us posted on the new mercury pot Alan, I will try to make it a goal of mine to have one of yours when it is financially sound for me, it is beautiful and well engineered.

[CasedImage]

Further to the post above about my pots I thought I’d share some final pics of the two pots I sent out today to clients. They differ from the pic posted earlier due to improvements and also from the final design I have settled on (sill start a new thread her in the dagforum for them).
These units for 110 and 220 mains voltage – they have the same parts but the elements are wired in series for 220v and in parallel for 110v, the controller having a wide band of input voltage.
With these I added insulation to the underside of the pots and clear acrylic walls to stop the cold air of the fume hood cooling the steel surface.
Cat for scale

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