Ferrous Attractions - What did Conservators experiment with at the AIC Annual Meeting?

In the last few weeks some questions have come up about testing magnetic systems and how to determine the proper system for mounting an artifact. While more and more conservators are turning to magnets (YAY!!!!) as a solution for mounting, there is still some information out there that may be confusing, here I hope to clear that up!

Below is a recap of the hands-on session conducted by Spicer Art Conservation at AIC's 2013 annual meeting. This hands-on session was an opportunity for conservators to test various types of magnets,  ferromagnetic materials (sheet metal, metal strips, embedded washers, etc) and gap materials (the artifact, mylar, display fabric, or other interleaving materials).  

About 80 participants were present for the early morning hands-on session. For those who were unable to attend AIC's 2013 annual meeting, or were at the meeting but were at other specially groups, here is just a quick summary of the session and the important outcomes observed by the various groups. Read the earlier blog post for a full description and details of the materials we used and how the tests were performed. The goal of the session was to become acquainted with the diverse variables of a magnet system. (1. The strength of the magnets; 2. The ferromagnetic materials; 3. The gap or space between.)

Conservators busy experimenting with magnets.

Small groups of 4 – 5 participants were created. Each group had a "jig" (a stand and a combination of a magnet system, and pre-measured weights to test the system with). Any combination of the system could be used. Fabrics, paper, Mylar, etc, were all placed between to act as a gap. Performing each trial 3 times was recommended, and then recorded onto a worksheet.

Wooden blocks were placed on the aluminum bar. Chains were then added to smaller blocks to hang clips. The clip supported the bucket for the weights. All of the weights were pre-measured sand-bags, in sizes of 5lb., 1lb., ½lb., and ¼ lb., as well as ½ oz.

Example of the block on the jig.

Below are images of the various blocks that were provided in each of the five groups. (A detailed description of the different components in each group is in the earlier post - see above for link.)

Local spot fasteners.

Steel gauge

Powder iron in several preparation methods.

Flexible ferrite magnets.

Velcro alternatives. (Read more about this system here.)

Observations

The final section of the session was when, as a group we were able to discuss our observations of the various trials. Each group was allowed to speak. Below are the recorded comments, with some of the most important comments in bold.

Test	Test Comments	Gap Comments
Green	One group recommended, “buy the cup!” While, they also mentioned that it left a mark or impression on the paper.	The felt/batting diminished the strength of the magnet’s strength. This observation represents the whole idea of: the thicker the gap, the weaker the pull strength.
Blue	The powdered iron embedded into the batting created the best results. Groups clearly saw that the increase in the concentration of iron powder held better. The 1” disc magnet in a cup did not hold more weight than the ½” disc in a cup on average. This was seen on all tests.	Mylar on the outside was better than when placed on the inside. This was noticed by other groups too. Nap-to-nap surface was better. Alluding to the fact that friction can play a role in the system.
Orange	The thin foil (.001) steel did not even hold the bucket. (The average weight was 40 grams) 24 gauge steel held the cup	When the Mylar was next to the steel, it failed at ½ lb. where as, when the fabric was placed next to the steel, it stayed at ½ lbs. Other groups also noticed this. Best results were when the suede was between and in the gap.
Red	The overall concession was that Flexible magnets do not hold much weight. One group was able to hold as much as 1-½ pounds using the 0.125 thick magnets.	All felt that the strongest was with the suede in the gap.
Yellow	Not a lot of sheer strength Magnet needs to be smooth when using the cup Mock-up is essential Discussion of how to adjust the lower lip of the “L” slat.	None

Participants quickly found that the amount and thickness of the ferromagnetic material greatly affected the strength of the magnet. This was seen no matter what form the ferromagnetic material was used in: washers, steel sheet, or powdered iron. Neither the foil tape (0.001), nor the powdered iron in the paint medium was found to be strong enough to hold the bucket with any of the magnets. Large differences in magnet size did not affect the pull strength (1” to ½” was the same) (See the table below).

With using a 1/2" disc, N42 grade neodymium rare earth magnet, the table below shows the range of weight values that the range of ferromagnetic materials can support. 

.001 steel	.01 steel	.025 steel	Fender	Thick washer	Painted	Epoxy mix	Embedded batting
Less than 40 grams	½ lbs	1 1/8 lbs	¾ lbs	1 lb	Less than 40 grams	~40 grams	1/8 lbs

The activity was designed as a learning experience while also serving as a fun introduction to magnetic systems. It appears that both were achieved. Participants were able to deal with many of the issues in creating and altering a magnetic system.

While some participants had prior experience with magnets, many were experiencing the magic of magnets for the first time. Many participants mentioned to me their surprise that there were so many magnets to choose from; they had no idea of the differences in size, shape, or strength, or even what a "rear earth magnet" really was. Many participants also mentioned that before the testing they envisioned certain trials to be more successful than others. For example, many confessed their disappointment in the strength of iron powder mixed with paint as they considered it to be a more achievable method for use in their museum and hoped to use that scenario. After seeing the low hold of the iron powder and the risk for slippage of the artifact, many confided that it seemed "too risky".

The other important feedback that came out of the hands-on session was from the conservators in the green group. They immediately saw the benefit of spreading out the "magnetic force" in a system we now call "large area pressure" rather than using an individual point system (i.e. small magnets placed at intervals). Their concerns were based around the possibility of an artifact becoming indented from using a magnet that was too strong. They had only considered mounting an artifact with magnets by placing the artifact on a ferromagnetic backing and simply placing magnets at intervals across its face. Not only did the hands-on session give them appreciation of testing a system before implementing the system, but they realized that they were not limited to using magnets in one single way, instead they could consider having magnets imbedded into the wall, while having a steel strip in the artifact.

The idea of leaving a magnet in an artifact brings up a very important topic. It was not until much later and after much research that we at SAC have started to design systems where the magnet is not kept in the artifact (read an earlier blog post). This is NOT because we determined it to be dangerous (although to our knowledge there is no published information to indicate detriment or safety), but it is really about the cost of magnets and the re-usability of a commodity that currently has environmental concerns (we will not go into it here, but if you are interested, do an internet search on the mining practices for rare earth metals and you will see much of it is done in China, and that it is done in a way that is not friendly to mother earth or the people who call her home).

The use of magnets in conservation is still very much in its infancy, but with good research and sound science, we can make remarkable progress towards utilizing the exciting and great potential magnets possess. Look for more of our blog entries on magnets and conservation in the future, we have a lot to say about magnets and hope that they excite you as much as they do us!

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Gwen Spicer is a textile conservator in private practice.  Spicer Art Conservation specializes in textile conservation, object conservation, and the conservation of works on paper.  Gwen's innovative treatment and mounting of flags and textiles is unrivaled.   Her current research focuses on the use of rare earth magnets in conservation. To contact her, please visit her website.

Learn more about magnets and their many uses in the new publications Magnetic Mounting Systems for Museums and Cultural Institutions. Available for purchase at www.spicerart.com/magnetbook.

Magnets, an alternative to Velcro?

by Gwen Spicer

Large textiles have been hung using Velcro since the 1970’s, with little change of technique. The first instructional handouts produced in the late 1970's, were from the Textile Museum and the Smithsonian Institution. The looped side of the Velcro is machine stitched to fabric, typically wide twill tape and then hand-stitched to the reverse side of the upper edge of a textile; while the hooked side is attached to the wall. However, over the years disadvantages of Velcro have come to light, like discoloration of the Velcro. In addition the loop-side of the Velcro that is sewn to the webbing and then hand stitched is quite bulky and poses difficulty with storage, whether rolled or boxed. In addition, stitching was not always a solution for all textiles.


Could magnets be an alternative, or even a substitute?  Several methods of using magnets as an alternative have been developed by conservators recently.

The philosophy and design to an alternative to Velcro when hanging large textiles remains the same.  A rule of thumb for Velcro is that it can support about 100 lbs per square inch (But this rule does not apply if the velcro has aged and the tiny hooks have deteriorated!).  Finding a magnetic system that equals this is less straightforward.  As stated in earlier posts, when using and selecting magnets of any type there are three key components that are in play. (see previous posts about magnets "Ferrous Attraction the Science Behind the Magic", et al, by clicking this link).  

1. The actual strength of the magnet itself.

2. The ability of the metal behind it to be magnetized.

3. The space between, or the gap created by the layers between the magnet and its receiving side.

Magnet components provided in the AIC Hands-on Session.

The challenge is that unlike paper, textiles can be quite heavy, creating a concern with downward pull of the artifact, or sheer stress of the system that results in failure or compression of the artifact at the magnet site. One of the groups in the hands-on session at AIC 2013 tested out a solution developed by SmallCorp Inc.

This solution that solves the weight uses an aluminum strip with a small lower lip (L-shaped in cross-section). Disc magnets, Grade N42, measuring ½” / ¾” dia. X 1/8”, with counter sunk holes are fastened along at 4” intervals on the vertical side. A 22-gauge steel piece is held into a stitched sleeve along the upper edge of the artifact. In this solution the lower lip actually holds the weight of the artifact, but it is the magnets that ensure that the steel piece is held back and onto the aluminum horizontal element. See the diagram below. 

¾” disc N42 Neodynimium magnets with counter-sink hole are screwed to a 
“L”-shaped aluminum bar. The magnets are spaced about 4” apart. The lower 
lip holds the 22-gauge steel that is secured in the sleeve and attached 
to the textile. The magnets keep the steel sheet back against the support.

The solution appears to be able to support substantial weight due to the lower lip. The secured magnets can be adjusted closer or further away from the vertical side, making the lip’s depth smaller if the protrusion is too large for any specific situation.

Two up close images of the "L" bracket

SmallCorp Inc. provides the metal components in the length that one desires (The "L"-shaped aluminum with the attached magnets and the powder-coated steel strip). The conservator or preparator creates the webbing sleeve for the powder-coated steel, just like one would for a Velcro system. Sewing the opening for the steel does need to be done with some precision in order to have a good fit. Then the webbing is stitched to the reverse side of the artifact. And you are ready to go!

The cotton webbing sleeve with the powder-coated steel
plate, secured to the aluminum "L"-shaped mounting bar.


_____________________________
Gwen Spicer is a textile conservator in private practice.  Spicer Art Conservation specializes in textile conservation, object conservation, and the conservation of works on paper.  Gwen's innovative treatment and mounting of flags and textiles is unrivaled.   To contact her, please visit her website.

Learn more about magnets and their many uses in the new publications Magnetic Mounting Systems for Museums and Cultural Institutions. Available for purchase at www.spicerart.com/magnetbook.

Ferrous Attraction and The Science Behind the Magic

by Gwen Spicer

At AIC's 2013 annual meeting in Indianapolis, Indiana, I presented a hands-on session on the use of magnets in conservation. Art conservators have been using magnets for many years, but mostly in a very limited way. Perhaps because a system has not been fully understood or described in literature, perhaps because it is not part of our training, or perhaps because it is a practice that is too new to be embraced. This session's purpose was to change all that and give conservators hands-on experience with my favorite things - MAGNETS!!!

Parts of the jig.

The jig put together.

Jig with a "system" in place. The wooden block is one side with a magnet, the metal behind is the other part. The red clip will hold a cup which will be filled with ever increasing weight until the system fails.

The focus of the session was for participants to learn and understand the parts of a magnet system so that they may use this knowledge in their own practice. Each part of the magnet system works in tandem in order to achieve the best combination for the artifact. The three parts are:

1. The strength of the magnet
2. The ferromagnetic material
3. The gap or space between the two

These three parts, in various combinations, were experimented with during the session.

Groups were divided into five puzzles or combinations of magnets and ferromagnetic materials. All of the groups were given the same materials to use to create various gaps. The jig works like so: weight is added to the system and then recorded when the system fails. (we are focusing on sheer strength of the magnetic system).

The goal of the session is to become acquainted with the diverse variables of a magnet system. A range of magnets of both Neodymium and ferrite flexible magnets were selected. The ferromagnetic material is also a range that includes several thicknesses of steel plate and preparations of iron powder.

Below is a table that describes the various tests. The Neodymium magnet for all cases were disc, grade N42 and 1/8" thick in a range of diameters. The poles were axially oriented.

Team	Receiving side	Magnet
Green – Local	Fender washer Thicker washer Metallic cups, ½” and 1” in cups	½”, ½” in cup, 1” 1” in cup
Blue – Iron Powder	Iron Powder “Magnetic” paint -       Painted on surface -       Mixed with Epoxy -       Embedded into Batting	½”, ½” in cup, 1” 1” in cup
Orange – Steel gauge	.001, .025 (24 ga), ½” in cup	¼”, ½”, ½” in cup,
Red – Flexible magnets	Foil tape (.001) .01 Steel (24 ga) Flexible magnet (0.06)	Flexible magnet (0.03) (0.06) (0.125)
Yellow - Velcro alternative idea	“Slat” Side Steel (24 ga) 3/4” dia attached to aluminum Empty cups	Removable Side • Webbing sleeve with pockets for magnets ½” • Steel (24 ga), powder-coated • 2 webbing sleeves

Several of these tests have been described in couple conservation publications. They were included for participants to see how not only how they worked, but more importantly, how they could be altered for another situation.

Each group recorded their findings using a real-time internet-based document. Then at the end of the session we discussed the findings. Click here for the final summary of results.

Time will tell, but I am sure once anyone has seen first-hand the power of magnets and can appreciate the ways in which they can be used, they will be as big a fan as I am. On a side note, if you want to see the use of magnets in a conservation project, be sure to check out the most recent edition of the AIC Journal which features a paper from yours truly demonstrating the use of magnets in an upholstery project with a Hunzinger chair.

Special thanks to SmallCorp, Inc who generously made all of the jigs and components for the session.  This session was only made possible because of them. My very deep gratitude goes to everyone there for being so helpful and supportive in making this session a reality.

_____________________________
Gwen Spicer is a textile conservator in private practice.  Spicer Art Conservation specializes in textile conservation, object conservation, and the conservation of works on paper.  Gwen's innovative treatment and mounting of flags and textiles is unrivaled.   Her current research focuses on rare earth magnets and their use in conservation. To contact her, please visit her website.

Learn more about magnets and their many uses in the new publications Magnetic Mounting Systems for Museums and Cultural Institutions. Available for purchase at www.spicerart.com/magnetbook.