I am interested in building an archivally sound painting. I have been told that a lead based ground will strengthen the oil paint all the way through the paint surface, and therefore is the most archivally sound way to build a painting. I would prefer to build it in other ways and am wondering if I can be effective in matching the performance of lead. Here are my methods: A rigid, cradled panel support behind an evenly stretched 16 oz tightly woven canvas, or a high grade linen, Gamblin PVA sizing, front and back of the fabric, Golden Acrylic Gesso, five coats (slightly diluted), underpaintings in undiluted Gamblin FastMatte Alkyd Safflower oil paints, a series glazes of Gamblin FastMatte paints, diuted to glaze consistance with Gamblin Solvent Free Fluid and applied with high paint spread.
From all that I have learned with research on your forum as well as talk with technical experts at both Golden and Gamblin, sizing is an important step to do before applying any ground if oil paint is to be used.
If an oil ground of any kind is being used, the sizing prevents the oil from penetrating the raw fabric. If a chalk or acrylic ground is being used, it prevents any binder seepage from either the front of the canvas (from cracks, fissures, spalls, scraping, sanding, bending, denting, pinholes or uneven application of the ground) or the back (from artist’s hands, etc.).
It looks to me, from what you have written, that MITRA recommends PVA as a sizing of equal merit to acrylic dispersion medium such as GAC100 or GAC400. From discussions with Golden, I learned that the GAC products should not be applied to the back of the fabric, because they are hygroscopic, and will rewet with atmospheric moisture, and stick what is below it, after the canvas has been stretched. This was the deal-breaker for me, on three fronts: 1) the sizing was hygroscopic which would lead to greater dimensional fluctuations of the canvas than with a non-hygroscopic sizing like Gamblin’s PVA. 2) I wanted to have any dimensional fluctuations that still did occur, happen independently of the cradled panel over which it was placed (stretched). In general building science, two materials that have different coefficient of thermal expansion rates should not be universally attached. Whole surface attachment, like gluing, does not allow relief from minor movements of the two substances, so causes undue stress resulting in things like buckling, spalling and cracking. 3) Indeed, I wanted the paintings on my canvases to be maintainable in the upcoming centuries, so any non-reversible glue – intentional OR unintentional – was not ideal. No glue at all was ideal in this regard.
Other considerations were that the GAC products went on and dried like plastic with greater sheen, and did not penetrate the fabric as much as the PVA. I surmise that the tooth decreases as the shine increases and therefore, I would suspect less adhesion. I also did not like the idea of inability to seal the backside. I suspect that things should either be sealed on all sides or no sides, if air, moisture or temperatures are to spread evenly, without causing instability.
When talking to Dave Bernard at Gamblin, he directed me to size both sides if using PVA so that the fabric fibres were fully saturated, and therefore encapsulated, preventing the possibility of rotting from inadvertent oil seepage as well as destabilizing moisture wicking.
I have done so, scrubbing the sizing in full strength evenly, to every fibre, with a stiff hog bristle short flat brush and scrubbing out any pooling, whatsoever. I do it on a flat surface only. I let the first side dry before sizing the other. This creates no buckling.
Upon discussion with Kristin deGhetaldi, I decided to stretch my fully sized and dry canvas over a fully untreated wooden cradled panel, using the same principle for the cradled wooden panel as for the canvas: full or no sealing. This would prevent warpage of the wood. Any off gassing from the wood to the painting is protected by the sizing. Any off-gassing or chemical penetration from wood sealers is also completely impossible aside from any sizing, because there are none.
Brian, upon these clarifications, how does this sound to you? Thanks so much for you help.
Hi Brian.
Indeed, there is evidence that the metal ions in lead can mitrate into adjacent layers of paint and strengthen them. You can find information in the Tumosa – Mecklenburg paper titled “The Influence of Pigments and ion Migration on the Durability of Drying Oil and Alkyd Paints”.
I hope this link works …
https://repository.si.edu/bitstream/handle/10088/20490/12.Mecklenburg.SCMC3.Mecklenburg.Web.pdf
Here is a quote from the abstract:
“But there is now considerable evidence that those metal ions are not only capable of migrating throughout a given paint layer but also sufficiently mobile to migrate from one paint layer to an adjacent one in a painting. In this case the migrating ions are capable of either enhancing or degrading the adjacent paint layers.”
In the case of lead, the ions are enhancing.
I am re-reading my post of February 19, 2018, and all the responses below it. As you know, I am hoping to work without toxins throughout my processes. I am seeking to know: can I create a stable painting without them? After laying out my specific questions for you to consider, I will describe my proposed modified approach, based on the answers you have given thus far.
Specific Questions:
Although lead white would add strength to the canvas, will the combination of my various processes create a more than adequate archival stability for my paintings over the centuries?
Specifically,
Can the rigid support (cradled panel) and the alkyd nature of my titanium white compensate for lead white usage in the ground and throughout my painting?
Can a traditional wet imprimatura compensate for the greater absorption of Golden Acrylic Gesso Ground? (I hope so – it seems to do a perfect job of it – performing for the artist during the process just as well as chalk gesso does – with perfect absorption level for the richer glaze layer and excellent surface flow for the subsequent lean paint).
Proposed Process:
Size a 16 oz. tightly woven raw canvas one side on the topside while fabric is flat on table. I prefer Gamblin PVA, for reasons already stated in a previous reply. Snap the fabric when wet to work out any wrinkles. Let dry a day.Evenly stretch canvas over a birch cradled panel, with the weft direction being vertical for maximum long-term support. Use non-rusting strong thumbtacks for easy potential conservation adjustments if ever required.Rewet the stretched canvas after stretching with PVA if there are still any wrinkles to facilitate the pullout of the fabric. Let sit a day.Hand rub and sand five coats of Golden Acrylic Gesso Ground, slightly diluted for smooth application.Allow to cure over several days.With Gamblin Solvent Free Fluid, dilute Gamblin FastMatte Alkyd Safflower Oil Foundation paint (mostly Burnt Sienna) no more than 25%. Rub on a high paint spread imprimatura-priming glaze with a cloth.Into the wet glaze, drop an undiluted foundational layer (grisaille) using Gamblin FastMatte Titanium White and Burnt Sienna and Ultramarine Blue (mixed to the same colour as Burnt Umber). Let dry several days.With virtually undiluted Gamblin FastMatte paints, add another foundational layer (Velatura). Let dry several days.Add several layers, several days apart, each starting with a glaze or scumble of the same paints diluted with no more than 25% Gamblin Solvent Free Fluid, with high paint spread. Then modify the glaze with additions of slightly diluted paint, or in white areas, undiluted paint. Palette: Gamblin FastMatte Alkyd Safflower Oil Paints:Titanium WhiteBurnt Sienna (in foundations)Quinacridone RedHansa Yellow (in foundations)Ultramarine BluePhthalo BlueRed Transparent Earth (in glazing applications)Rembrandt Oil PaintsTransparent Yellow (in glazing applications)
I am looking forward to your answers. Thanks so much for all you do and for your clarifications here.
I am re-reading my post, and all the responses below it. As you know, I am hoping to work without toxins throughout my processes. I am seeking to know: can I create a stable painting without them? After laying out my specific questions for you to consider, I will describe my proposed modified approach, based on the answers you have given thus far.
Specific Questions:
Although lead white would add strength to the canvas, will the combination of my various processes create a more than adequate archival stability for my paintings over the centuries?
Can the rigid support (cradled panel) compensate for lead white usage in the ground and throughout my painting?
Can a traditional wet premature compensate for the greater absorption of Golden Acrylic Gesso Ground? (It seems to do a perfect job of it – performing during the process exactly like chalk gesso does – with perfect absorption level for the richer glaze layer and excellent surface flow for the subsequent lean paint).
Proposed Process:
Size a 16 oz tightly woven raw canvas one side on the top side while fabric is flat on table .I prefer Gamblin PVA, for reasons already stated in a previous reply. Snap the fabric when wet to work out any wrinkles. Let dry a day.Evenly stretch canvas over a birch cradled panel, with the weft direction being vertical.Rewet the stretched canvas with PVA if there are still any wrinkles to facilitate the pullout of the fabric. Let sit a day.Hand rub and sand five coats of Golden Acrylic Gesso Ground.Allow to cure over several days.With a 25% diluted Gamblin FastMatte Alkyd Safflower Oil Foundation paint, rub on a high paint spread imprimatura-priming glaze with a cloth.Into the wet glaze, drop an undiluted foundational layer (grisaille) using Gamblin FastMatte Titanium White and Burnt Sienna and Ultramarine Blue (mixed to the same colour as Burnt Umber). Let dry several days.With undiluted Gamblin FastMatte paints, add another foundational layer (Velatura). Let dry several days.Add several layers, several days apart, each starting with a roughly 25% diluted glaze or scumble of the same paints, with high paint spread, the glaze subsequently modified with additions of slightly diluted paint, or in white areas, undiluted paint.
I am looking forward to your answers. Thanks so much for your clarifications.
Kathy Marlene Bailey
There are a few points here that need clarification. Lead white is the most flexible oil primer and is responsible for the continued existence of many old master paintings. It is the continued flexibility of the lead white oil ground that contributes to the survival of subsequent paint layer. It does not really chemically change later paint layers making them more resilient. This beneficial effect is most obvious when painting on flexible supports as they are the most responsive to changes in relative humidity. You are proposing stretching your fabric over a rigid support which with will go a long way to protecting your work from physical damage due to impacts and will serve as an environmental buffer, slowing down the effects of changes in humidity.
As to sizing, I see no benefit to using PVA size under an acrylic dispersion ground, although it would probably be fine. PVA is generally used under an oil ground as a replacement for animal glue.
If it were me I would use an acrylic dispersion medium as a size (see out “Resources” section on sizes) since that will be the binder in the ground and will behave in a similar manner. It also seems to create a more rigid fabric support. Perform a search on MITRA discussing the difference between acrylic dispersion and PVA sizes.
I wonder why and how you intend on sizing both sides of the fabric. If it were me, I would either adhere the fabric to the pane with the acrylic medium or if you wanted reversibility, which is understandable, I would first size the surface of the panel, allow it to dry, then stretch the fabric over the panel, and then size the surface of the fabric.
The reason I write this is that it is difficult, or at least laborious, to size both sides of the fabric without creating buckling which is difficult to remove during stretching. This can be done, but it requires that you stretch a slightly larger piece of fabric on a working stretcher that allows access to both sides. You apply the size to one side and then the other while the first is still wet. Let this dry and apply another coat on both sides in the same manner. Let the whole dry overnight. Remove from the working strainer and stretch over the panel before applying the ground. This process is far more likely to produce a planer surface.
I see no problem with your proposed paint layers.
Finally, I cannot say if this system is an exact substitute for a painting on a lead white ground, but it does sound like a sound method.
I have sent a note to representatives at Gamblin to weigh in on this.
We view sizing the back of fabric supports as a means to further reduce absorbency of the fabric and seal is off from atmospheric moisture. As Brian mentioned, this work will be done by the rigid support backing in your case. PVA Size underneath acrylic gesso is superfluous in the structure you described. I do, however, advocate for the use of oil/alkyd ground rather than acrylic gesso, as oil/alkyd grounds are less absorbent. Oil colors are formulated to have an appropriate balance of pigment and oil for any given color, which effects color strength, texture, surface quality as well as flexibility of the resulting paint film. Absorbent grounds will through off this balance and generally reduce the flexibility of paint layers. I cannot speak for all oil/alkyd grounds on the market, so I am referencing Gamblin Oil Painting Ground here.
Kind regards,
Scott Gellatly
Product Manager Gamblin Artists Colors
To the OP, re-reading your post I just noticed that you mentioned chalk ground on canvas. Please note that a chalk-glue ground sould not be used on canvas as it is far too brittle for a flexible support. The only time this would be appropriate is when the fabric is completely glued to a rigid panel and the fabric is then completely covered with the chalk-glue ground. In this structure the fabric is acting as an interlayer and is not really carrying the weight of the ground and paint.
I will answer on behalf of Brian as well here. He is well aware of the fact that lead can form metal soaps…as are many of the moderators on this forum. However when one is talking about zinc containing films vs. lead containing films there is hardly a comparison when dealing with film strength and flexibility. Zinc is known to cause paint/ground layers to become increasingly more brittle over time (note this has really only been observed in oil-containing films to date NOT acrylics). There are extreme examples of lead soap formation however where the soaps have actually migrated to the surface of the painting and “erupted,” causing all sort of unappealing micro-craters to form. But the number of Old Master paintings that possess lead-containing pigments that are in great shape is significant…realize that a certain number of lead soaps are needed to actually impart film strength and flaxibility.While there has been an exhaustive amount of research regarding lead soaps (almost too much imo) we still have yet to learn about what causes these metal ions to migrate to the surface and cause the unaesthetic look I described above. There is some evidence that this phenomenon can be linked to high levels of humidity and/or exposure to higher temperatures….which leads me then to the big question as to how traditional lining and consolidation techniques may have impacted the migration of lead soaps. In the past, restorers would frequently use aqueous-based adhesives combined with heat to consolidate flaking paint and to line paintings. Finally, we still have yet to look into how flooding one’s paint with lead driers can affect this issue (again I raise my eyebrow at this given the fact that so many studies have been done on lead soaps….WHY this has not been explored is beyond me). Just wanted to clarify a few things and add some additional info as to where we are regarding the lead soap phenomenon. It is almost an entirely different beast than when dealing with zinc….I would much rather have to deal with an Old Master painting that has a few tiny unsightly micro-craters (that can be inpainted out with reversible conservation colors) than an oil painting that is globally delaminating because it is on a zinc white-oil ground.
Kristin’s has written a very complete answer here. What you point out is certainly technically true. Its effect in this instance would probably be minimal and I neglected to bring it into the discussion. I attended when Mecklenburg presented this information. I was responding to a separate issue and did say that lead is preferable but that what the OP proposed appeared sound. Thanks for bringing this topic into the discussion.
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