Hello, A couple of quick questions from a fairly new mountmaker here. I've been asked to research the use of weighted bags for stabilizing ceramic pots/vases on exhibit. Has anyone has ever used this method? If so, what perimeters did you use to determine which of these types of objects could use them? What worked and what didn't? Are there any tips/issues to watch out for? Also, I'm looking for suggestions on how to handle lidded objects. Do most rely on the lip inside the lid to simply keep it in place, or is there an internal mount that can be fabricated? Any advice, suggestions, or sketches given will be greatly appreciated. Thank you so much!
All the time. We have a huge collection of Rookwood pottery and if it is inside a case out of the reach of visitors we use weighted bags. I steer this directions when the object has a good foot but, seems a little top-heavy.
We have multiple sizes of bags/snakes made with different types of weights. Some have sand inside and others have lead shot. Typically square like a cornhole bag, sometimes elongated, like a snake to use when transporting unstable objects on carts inside the galleries. Most are made of soft linen, but we have older ones made of what feels like suede. They have just always been here and been in use before I started this job, so I keep using them.
Lids… if they seem stable and don’t rattle we just place them on the object. If it seems like it will rattle every time someone walks by try using museum wax. Check with a conservator first but, we use a product called Rhoplex N-580. It comes as a milky white liquid but, it dries clear. If you use an eye dropper and contact release mylar you can drip out tiny dots. Peel and use tacky little dots. It has many other uses.
PJ Grimm | Preparator
t 513-639-2010 Email: email@example.com
Cincinnati Art Museum we bring people and art together
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Ballasting objects is definitely one of the best ways of stabilizing them for a temblor. The basic rule is: the lower you get the objects center of gravity the better...which seems obvious enough. The reason I mention it is that just adding any kind or amount of weight won't get you there. ... depending on the shape of the object adding weight could just be adding mass and not really doing anything to create stability. This is the reason lead is a better stabilizer than sand. Since it has a greater specific gravity than ceramic it will sit lower in the pot for the same amount of weight added. If you would like a deeper analysis on stability there is this simple formula:
for an object 6' x 1' @ 200 pounds:
Weight = 200 pounds
Depth to CG = 6 inches
Force = 60 pounds
Height @ CG= 36 inches
Of course you will need to calculate the expected force but other than that you should be able to get all the other information. As is shown since the Force to height calculation is greater the object is unstable. In this case you should add ballast until the numbers come to an acceptable range. For more see page 27 of this article: http://s3.amazonaws.com/aam_phase2/pdf_assets/files/000/000/398/original/TheArtOfmakingMounts_Avalos.pdf?1441403073
In general though if you can easily handle an object with your hands you can tell if the object can easily right itself beyond a 45 degree angle. In most cases this is sufficient to determine an objects stability and whether adding weight will be very helpful.
Asian Art Museum
Hi Kristi, For the most part I have always ended up making a mount that rides up the back and hugs the vessel at it's neck, but if it has a wide enough base and the mouth is big enough to allow a hand to place a bag then we have also used weighted bags. I have made them out of poly zip seal bags filled with sand or lead shot. once the bag is filled I staple it and insert it into a secondary bag zip side first, Basically you are double bagging. With the lids it depends on what the conservator recommends in some cases I've floated the lid using a mount coming from the wall or we have place thin strips of ethafoam between the lid and lip.
Milwaukee Public Museum
This is a photo of the type of bag I make for simple weighting of pots.
It’s lead shot double bagged into 2 polyethylene bags then into black photo fabric,( that somehow passed our Oddy test.)
The black hides well in pots and doesn’t reflect light. The little loop is so that I can tie a tether onto the bag . If a pots opening is tight, I reach in with chop sticks and pull the tether out then pull the bag out by the teather.
Here are some custom shaped bags with fine sand and the tethers (Blue twill tap) for this very cool Chinese ewer.
Other recipients: firstname.lastname@example.org Thanks for sharing everyone! On the fabric, I'm also looking into making the weights. I've got a supplier for the lead shot, and poly, but am still shopping around for the stockinette material. I know Benchmark sells it, but is there another supplier with a better price, or another type of fabric that has passed the Oddy Test? Thanks again, Kristi
Paul Brower 1/19/17
Hi Kristi, I get stockinette from a local medical supply store. There are 5 store in my small/medium town. Most sell it by the yard or the box if you need a lot. Paul