I may be a blog whore, but I love this blog the most. I have started posting on a new blog at http://site.yque.com/word using a wordpress format. It does not mean that I am abandoning this blog, but frankly the world has abandoned blogs so it may not really matter. Blogging has been reduced to a primitive form of communication and it's usefulness may be the same as a diary, for personal use only. The format here is simple, which I like, but it may be too simple to allow for growth. I think of this place as a rambling technical jargon world where I can mumble while I drink about epoxy, resins and other fast setting materials. It is the dream world of magic that lies in the chemicals that are pigmented and toned into something that may resemble something else and it is here that I can transliterate the intent.
I am challenged by the newer tools, like facebook and twitter, "Why?", I say. "Why?" Do people not know how to make web pages, but they have to rely on 3rd party software to organize their lives. FTS (FUCK THAT SHIT) if that is not already an acronym. I don't see any benefits to the limitations that exist in a pre-organized format for social relationships in th digital world. I don't have a valid reason why it isn't good, but I don't have a reason why it is good either. It is like I can't be personal if I feel that I am literally in a pre-formatted So check out http://site.yque.com/word because I won't be posting here quite as often.
Saturday, October 15, 2011
Sunday, October 2, 2011
Hidden Values have no Value - Epoxy Clear Coating takes away the texture effects
The riddle, hidden values have no value, means that many of the processes I have used to get to my final product are now ending up being hidden under a layer of epoxy, which provides a great finish. I have been doing casting with resin and plaster and printing using vinyl and acrylics which have come together as a finished rectangular framed pieces. Although I have built walls with these framed frescoes as I call them, because of the plaster, but when I fit several frames together I have been able to make small tables that look ikea like modern. The effect that makes them seem useful as a table is the final coat of epoxy, as a clear coat, and this also works to smooth out the top surface. Once this clear coat of epoxy is applied, then all of the effects of the raised plaster and printing as flattened into the base.
The flat effect of the table top means that all of the work I have put into the fresco under the epoxy seems wasted. I could just as easily printed out a picture and pasted it to the top of the frame and gotten the same effect. I can tell there is something going on underneath the epoxy, but I don't think anyone else would really care. I do think over the long haul, 20-50-100 years, the benefits of the plaster under the epoxy will hold up to any exposure to elements and to long term exposure to UV, better than a print out of a piece of paper would. Actually, I am not sure that the durability comment is even true since to destroy the paper you would have to go through the epoxy.
The few benefits of the photo fresco versus the decoupage technique is that the epoxy bonds quickly to the plaster, whereas paper seems to unevenly absorb some of the epoxy and it can create inconsistencies in the appearance of the underlying work. I have been resigning myself to consider each thing as totally different and simply moving forward with making as many clear coated pieces as I can using print outs just to get more finished work out there. I just have a hard time breaking down and doing things that way as I love the process that the screen casting photo frescoes create. Fact is the decoupage technique will help me clear out my old screens sooner and that is the biggest issue since I have so many screens left over from my years doing t-shirt printing jobs.
Recently I have been using larger frames for the photo fresco prints and this is very satisfying work as I can place a photo image in the center and build a brick wall pattern around the photo, then later cast in the plaster or duracal, tinted to be the color of brick, and this provides a pattern background that gives the feeling that the photo is on a wall, literally. I haven't clear coated one of these larger pieces yet, but I have been buying one frame a week to do this with and so far this is my favorite wall hanging type of work because of the size and the fact that the photo is not the main element. Also these frames already have two holes drilled into them and are quite thin, so I feel that as a frame it can present itself without having to be adorned with additional wood or finish work.
I have been reinforcing these larger pieces on the back with acrylic and burlap, so I also feel I could use these pieces to build a wall with the backside being the interior part of a structure. The exterior part of the piece has all the character of a plaster wall and I think they could hold up under some severe exposure to UV, rain and whatever else may come the way of our mild, but wet winters in Northern California. The point of this is that as long as I focus my photo fresco attention on these larger pieces, it might free me up to make more of the decoupage type pieces and not worry about the fresco techniques that are not realized with my current methods.
The flat effect of the table top means that all of the work I have put into the fresco under the epoxy seems wasted. I could just as easily printed out a picture and pasted it to the top of the frame and gotten the same effect. I can tell there is something going on underneath the epoxy, but I don't think anyone else would really care. I do think over the long haul, 20-50-100 years, the benefits of the plaster under the epoxy will hold up to any exposure to elements and to long term exposure to UV, better than a print out of a piece of paper would. Actually, I am not sure that the durability comment is even true since to destroy the paper you would have to go through the epoxy.
The few benefits of the photo fresco versus the decoupage technique is that the epoxy bonds quickly to the plaster, whereas paper seems to unevenly absorb some of the epoxy and it can create inconsistencies in the appearance of the underlying work. I have been resigning myself to consider each thing as totally different and simply moving forward with making as many clear coated pieces as I can using print outs just to get more finished work out there. I just have a hard time breaking down and doing things that way as I love the process that the screen casting photo frescoes create. Fact is the decoupage technique will help me clear out my old screens sooner and that is the biggest issue since I have so many screens left over from my years doing t-shirt printing jobs.
Recently I have been using larger frames for the photo fresco prints and this is very satisfying work as I can place a photo image in the center and build a brick wall pattern around the photo, then later cast in the plaster or duracal, tinted to be the color of brick, and this provides a pattern background that gives the feeling that the photo is on a wall, literally. I haven't clear coated one of these larger pieces yet, but I have been buying one frame a week to do this with and so far this is my favorite wall hanging type of work because of the size and the fact that the photo is not the main element. Also these frames already have two holes drilled into them and are quite thin, so I feel that as a frame it can present itself without having to be adorned with additional wood or finish work.
I have been reinforcing these larger pieces on the back with acrylic and burlap, so I also feel I could use these pieces to build a wall with the backside being the interior part of a structure. The exterior part of the piece has all the character of a plaster wall and I think they could hold up under some severe exposure to UV, rain and whatever else may come the way of our mild, but wet winters in Northern California. The point of this is that as long as I focus my photo fresco attention on these larger pieces, it might free me up to make more of the decoupage type pieces and not worry about the fresco techniques that are not realized with my current methods.
Thursday, September 29, 2011
What if all the things I tried before worked now?
Generations have passed since I have last posted. There is an Ipod 5 out now. There is a new recession, possibly even a new President. Also there have been several new developments in my photo-fresco endeavors.
Except for all the technical stuff, one newer change is that I have started using some of my own photos for the content. The images are not as iconic as some of the famous people and symbolic shapes that I usually hack together, but in some sense this has added a personal touch to my work. I will discuss the relevance to my photographic and screenprinting edeavors later.
Secondly I have reintroduced the idea of making the final pieces into tables. I tried this earlier, but didn't like doing all of the finish work required to make a table work and be flat. I have since simplified the process and am using aluminum frames that bolt together nicely. These aluminum frames come from my screenprinting work, so they are recycled, but they also add a modular elegance, sort of modern looking and strong.
Thirdly, I have found ways to keep the brick wall concept in this work. By working on larger pieces I can suspend the photographic print image in the center while finishing a brick pattern around the graphic, thus making the piece fell like a photo made into, or pasted onto a brick wall. Most recently I have started finishing the smaller pieces to the edge of the rectangular frame with red plaster, thinking of each smaller piece as a brick itself, that does not require the grout pattern of an entire wall. This may force me to work more with horizontal images for the smaller work with the idea of placing them into larger walls.
Finally I have merged all of my materials in a way that baffles me, but it works. Screen printing inks, gypsum plaster, acrylic gesso, burlap canvas, silicon molds, wire mesh stencils and clear epoxy. Each piece does not require all of these, but together they make what I am calling photo-fresco. I have been considering the use of the work screen-casting as some of the pieces are filled with plaster and in a sense they are castings, but the photo-fresco phrase seems to have a sensible meaning.
Tuesday, August 2, 2011
I now have a wall, but what next?
I took my portable brick wall to Los Angeles and set it up in the back of Y-Que Trading Post in Los Feliz, Hollywood, California. It is discreet and blends in with the back of the store. This piece does not cry out, LOOK AT ME!, but is more of an I Am Here With You type of thing. It is not definite, yet it is solid. There are objects to focus upon, but they are not the totality. In fact I cannot even say that I can define the wall except in pieces, and then that does not work because the wall pieces will change over time. Whenever someone mentions it in my presence I try to draw them to the back to look at the infrastructure, which is of no concern to most. I feel I may have gone somewhere with this piece and where it is seems important, in that I have lifted the cement of Hollywood 90 degrees to a vertical position. There are the Hollywood Stars, which are on the ground and people walk on them and are forced to look down. Also there is Gromann's Chinese Theatre which has imprints and signatures in cement, but again it is horizontal and people step upon the work and must look down to see the work. The potential for my new work is to bring into wall form similar symbols that are culturally relevant, through the media, but give these characters that cry out for respect and meaning a new way to be entombed. I am hesitant to push celebrity images into my wall, but this may be necessary to give it cultural meaning. Thank gosh I have so many mugshots of celebrities that I can work with to push this idea. I am currently restrained by the amount of time I can devote to my side projects, but if I consider what is important with my work I can find the time to fill more space with photo fresco brick images. I am also considering a brick sticker campaign, for but marketing reasons. My time is the summer and projects are what I do, so something that won't get me thrown in jail for vandalism is workable and stickers are just not a convictable offense.
Thursday, July 21, 2011
Why not use polyester resin directly and epoxy
For straight casting it may be better to just use the epoxy and forget about all of the plaster and cement. I could cast the top layer first with clear epoxy, then paint in the back with the cement images in reverse order and don't use any cement or plaster. The reason that this won't work is that epoxy seems to need something to hold onto and it may change shape and become fluid in heat, therefore as a thin layer epoxy is good as a coating, but not so good structurally and something strong under it is best, whether it is wood, plaster or cement. Plus the epoxy would require painting in reverse order and that would just take away from the fun of making these pieces as I have been developing my techniques and in some cases I don't even have to paint my finished work, like with the cast brick wall patterns in the screen printing frames.
Painting can be considered a final coat, instead of an epoxy layer. In many cases I am spray painting color and added effects like brick lines by spray painting onto the cast materials like the Duracal gypsum plaster cement. The paint, if it is bonded well, is essentially a sealant, a top layer of protection from UV and rain, but I don't fully trust it. Mostly because paint scratches easily and will rapidly wear away with weathering, as can be seen on the many murals around Los Angeles. So except in mild conditions or for short periods of time, spray painting is not a satisfactory sealant by itself. I have used spray painted clear coats on top of epoxy, but the smell and blurriness that ensues is not worth it.
Double sealing by coating the back and the front is not to be done. If I have learned anything it is not to completely seal anything. If you do then the moisture that is built up inside with eventually destroy an item from the inside, so I have resisted the desire to paint the back of my pieces or to add an extra layer to the back, unless I leave the front unsealed. Ideally, my pieces are not completely sealed in that the wood on the edges can absorb moisture, but how would the water know to migrate to that part of the frame? Possibly the capillary action of the wood could draw the water from the plaster over time and work as a sponge, but I don't feel comfortable with this for now, although it is intriguing.
The wooden frames are serving as bumpers for the castings and in the past I have had trouble with the piece drying out and dropping from the frames. However, I have since worked in reinforcement and anchors regularly to keep this from happening. I broke apart one piece the other day and first off I was able to walk on it without it breaking and secondly with I tried to break the individual piece it literally broke the wire mesh inside instead of separating along any specific line. Therefore the reinforcement with plasters should make the pieces hold into the frames for years, or until the wood itself rots away. I am no longer putting decorative top frames on my pieces as they tend to get broken in transport and now that I am anchoring the pieces more successfully I don't think the top frames are needed to act as a bonding agent or washer against the wood.
I have been testing aluminum frames, but I have so many wooden frames in storage I still consider this testing and a future application. I have to keep going forward with using up the thousand or so wooden frames I have in storage to escape the trap I have created for myself by doing so much commercial work with screen printing over the years. In a way this is my punishment for being successful as a business person in that I have built up an archive of old frames with screen printing designs on them and most of my efforts with photo fresco prints has been to find an application that can use up these frames. Now I am buying aluminum frames for my screen printing, but I still need to recycle these frames instead of just taking them to the dump, cleaning them out and reusing them or continuing to pay rent for them in a storage unit in the desert. The wall is the best use I've come up with so far, although then I am going to have to store the wall, but hopefully I can build a house or fence out of the wall and then just watch it wear away over time.
Painting can be considered a final coat, instead of an epoxy layer. In many cases I am spray painting color and added effects like brick lines by spray painting onto the cast materials like the Duracal gypsum plaster cement. The paint, if it is bonded well, is essentially a sealant, a top layer of protection from UV and rain, but I don't fully trust it. Mostly because paint scratches easily and will rapidly wear away with weathering, as can be seen on the many murals around Los Angeles. So except in mild conditions or for short periods of time, spray painting is not a satisfactory sealant by itself. I have used spray painted clear coats on top of epoxy, but the smell and blurriness that ensues is not worth it.
Double sealing by coating the back and the front is not to be done. If I have learned anything it is not to completely seal anything. If you do then the moisture that is built up inside with eventually destroy an item from the inside, so I have resisted the desire to paint the back of my pieces or to add an extra layer to the back, unless I leave the front unsealed. Ideally, my pieces are not completely sealed in that the wood on the edges can absorb moisture, but how would the water know to migrate to that part of the frame? Possibly the capillary action of the wood could draw the water from the plaster over time and work as a sponge, but I don't feel comfortable with this for now, although it is intriguing.
The wooden frames are serving as bumpers for the castings and in the past I have had trouble with the piece drying out and dropping from the frames. However, I have since worked in reinforcement and anchors regularly to keep this from happening. I broke apart one piece the other day and first off I was able to walk on it without it breaking and secondly with I tried to break the individual piece it literally broke the wire mesh inside instead of separating along any specific line. Therefore the reinforcement with plasters should make the pieces hold into the frames for years, or until the wood itself rots away. I am no longer putting decorative top frames on my pieces as they tend to get broken in transport and now that I am anchoring the pieces more successfully I don't think the top frames are needed to act as a bonding agent or washer against the wood.
I have been testing aluminum frames, but I have so many wooden frames in storage I still consider this testing and a future application. I have to keep going forward with using up the thousand or so wooden frames I have in storage to escape the trap I have created for myself by doing so much commercial work with screen printing over the years. In a way this is my punishment for being successful as a business person in that I have built up an archive of old frames with screen printing designs on them and most of my efforts with photo fresco prints has been to find an application that can use up these frames. Now I am buying aluminum frames for my screen printing, but I still need to recycle these frames instead of just taking them to the dump, cleaning them out and reusing them or continuing to pay rent for them in a storage unit in the desert. The wall is the best use I've come up with so far, although then I am going to have to store the wall, but hopefully I can build a house or fence out of the wall and then just watch it wear away over time.
Gypsum Plaster Products versus Portland Cement Products
Without getting into the chemistry about why one of these types of products is better than the other I have just started testing them in my pieces to see which ones I like. Personally I am overwhelmed by the many different types of cements that are available at my local hardware stores, not to mention the mortar isles, I haven't even been able to start in that section. Truly I don't know the difference between mortar and cement, other than one must be made for adhesion and the other for durability and strength. The mixtures between portland cement, sand and additives seems to largely make up the differences between the materials. Price is my concern and the ability of the cements to make detail in a mold, so I haven't found many workable solutions that include any type of aggregate when it comes to the portland cement products. Mortar has no aggregate, but the cracking when it is poured at 1/2" or more increases, so I have decided to stay away from the mortars for now.
The biggest problem with portland cement based products verus the plaster gypsum based products is shrinkage. Cement shrinks, even the expensive stuff. I've been working with "Cement All" at $18 for a 55 lb. bag and although the cracking is down to a minimum, it still appears to shrink around the edges. I have anchored the pieces before I pour the Cement All mixture, as well, I have put in a reinforced wire mesh to strengthen the casting, but I don't want to have to rely on the mesh and anchors as a way to keep my pieces in place and even with an epoxy coating on top to help with the bonding, I find myself back to square one which is why use durable materials if I have to seal them in a clear bullet-proof case to make them work?
Ideally the concrete may get it's strength from the shrinkage as the water is displaced and the molecules harden into durable structures that can exist outside in the elements. Also the strength may allow the material itself to resist cracking in normal temperature fluctuations, so there are some good factors about portland based cement products that have kept me from giving up. Stucco was another material that I have been playing with, but as I use it more and more I don't see really the advantage of it over other acrylic polymer based gypsum based products and I don't seem to get the detail out of the stucco that I do with the plasters. I have also forgot to mention the setting times are longer with the cements, even the quick ones, as compared to the plasters.
This brings me back to the Gypsum plaster based products and the one that seems to work like cement, but expands like plaster is Duracal. Grey in color I have mixed it with red cement powder and have gotten a nice brick color. Duracal seems to be strong and sets very quickly, unlike the cements. The detail when casting with the Duracal is as good as with the other plasters like Hydrocal, Forton MG and Tufstone. Tufstone is my favorite white based plaster that has microfibers mixed in and an acrylic polymer, but neither of these items may be as durable as cement without coating them and covering them with sealants.
Having completed my first Wall of Photo Fresco pieces, as shown in a prior post, I realize that weight may be a larger factor than strength. The pieces I have been making with the cement were made with the idea of being about to be placed in the ground, like bricks for a walkway, only with images molded and cast into them. I took these same items that can hardly be picked up and used them as a the pieces in my photo fresco wall and the weight of the wall scares me. I can see this think falling over and killing me as some sort of artistic justice in that I keep trying to make something that will last a long time, so it inadvertently shortens my lifespan proportionately. Now I live in fear of my wall as I have tied it to the strongest thing in my yard, and unused weight lifting device that is too heavy to get rid of. I may not lift weights, but lifting and moving these photo fresco castings all day is indeed a workout.
The weight of the wall is something that I must deal with and this seems to lead to the obvious conclusion that the thickness must be reduced. I spoke with an engineer about how thick concrete needs to be to be able to be walked on and 2 1/2 inches is a basic measure, so I have been back filling these castings with thicker layers of aggregate based cement to give them the option of being able to be used as counter tops on tables or a walking bricks, sort of like the Hollywood stars in LA, but my style. This added weight also means more material, which in the end offsets any savings that come from the cheaper Portland cement based products. Unless I can find a cement that does not shrink and is truly crack resistant then I need to go back to the high tech plasters, like Duracal and make thinner walls that weigh less once they are made.
My son has finally found a practical use for this wall as he thinks that he can use the wall as a practice board for throwing lacrosse balls at, well, this may not work with the thinner structures, but if the wall can withstand that type of abuse then I can use that as a measure of success. At least as he propels the rubbery heavy balls to the wall he won't be standing under it, so the risk of the wall falling on him is less. Still I don't trust the weight and I can't see any way to make the photo fresco wall without using lighter materials, even if they require additional exterior coats to make them durable and resistant to the elements.
The biggest problem with portland cement based products verus the plaster gypsum based products is shrinkage. Cement shrinks, even the expensive stuff. I've been working with "Cement All" at $18 for a 55 lb. bag and although the cracking is down to a minimum, it still appears to shrink around the edges. I have anchored the pieces before I pour the Cement All mixture, as well, I have put in a reinforced wire mesh to strengthen the casting, but I don't want to have to rely on the mesh and anchors as a way to keep my pieces in place and even with an epoxy coating on top to help with the bonding, I find myself back to square one which is why use durable materials if I have to seal them in a clear bullet-proof case to make them work?
Ideally the concrete may get it's strength from the shrinkage as the water is displaced and the molecules harden into durable structures that can exist outside in the elements. Also the strength may allow the material itself to resist cracking in normal temperature fluctuations, so there are some good factors about portland based cement products that have kept me from giving up. Stucco was another material that I have been playing with, but as I use it more and more I don't see really the advantage of it over other acrylic polymer based gypsum based products and I don't seem to get the detail out of the stucco that I do with the plasters. I have also forgot to mention the setting times are longer with the cements, even the quick ones, as compared to the plasters.
This brings me back to the Gypsum plaster based products and the one that seems to work like cement, but expands like plaster is Duracal. Grey in color I have mixed it with red cement powder and have gotten a nice brick color. Duracal seems to be strong and sets very quickly, unlike the cements. The detail when casting with the Duracal is as good as with the other plasters like Hydrocal, Forton MG and Tufstone. Tufstone is my favorite white based plaster that has microfibers mixed in and an acrylic polymer, but neither of these items may be as durable as cement without coating them and covering them with sealants.
Having completed my first Wall of Photo Fresco pieces, as shown in a prior post, I realize that weight may be a larger factor than strength. The pieces I have been making with the cement were made with the idea of being about to be placed in the ground, like bricks for a walkway, only with images molded and cast into them. I took these same items that can hardly be picked up and used them as a the pieces in my photo fresco wall and the weight of the wall scares me. I can see this think falling over and killing me as some sort of artistic justice in that I keep trying to make something that will last a long time, so it inadvertently shortens my lifespan proportionately. Now I live in fear of my wall as I have tied it to the strongest thing in my yard, and unused weight lifting device that is too heavy to get rid of. I may not lift weights, but lifting and moving these photo fresco castings all day is indeed a workout.
The weight of the wall is something that I must deal with and this seems to lead to the obvious conclusion that the thickness must be reduced. I spoke with an engineer about how thick concrete needs to be to be able to be walked on and 2 1/2 inches is a basic measure, so I have been back filling these castings with thicker layers of aggregate based cement to give them the option of being able to be used as counter tops on tables or a walking bricks, sort of like the Hollywood stars in LA, but my style. This added weight also means more material, which in the end offsets any savings that come from the cheaper Portland cement based products. Unless I can find a cement that does not shrink and is truly crack resistant then I need to go back to the high tech plasters, like Duracal and make thinner walls that weigh less once they are made.
My son has finally found a practical use for this wall as he thinks that he can use the wall as a practice board for throwing lacrosse balls at, well, this may not work with the thinner structures, but if the wall can withstand that type of abuse then I can use that as a measure of success. At least as he propels the rubbery heavy balls to the wall he won't be standing under it, so the risk of the wall falling on him is less. Still I don't trust the weight and I can't see any way to make the photo fresco wall without using lighter materials, even if they require additional exterior coats to make them durable and resistant to the elements.
Long Time No Plast ...er that is.
I haven't been posting regularly about my progress and work with casting reliefs, screen painting and photo fresco works as I keep testing new materials and until now I have been too caught up in the work to report to headquarters. As a result I will post a bunch of material in short burst with some accompanying photos, not in any particular order. My latest experiments have been with using cheaper materials like Portland Cement based mortar, stucco and cements to try increase the waterproof character of my pieces.
Water resistant, water proof and ultimate durability go hand in hand. The most toxic element in regular outside exposure is water, through mist, fog, rain, and basic humidity. Temperature change is also an invisible factor that changes the shape of items throughout a day. Strength within an item may resist the shape-shifting, but the porosity of an item also allows saturation which in turn may cause materials to breakdown. Sealing a piece is also a way to stop water from getting into an item, but my understanding is the if an item is completely sealed temperature changes will still make the materials that are used increase and decrease in size throughout a range and this is what can cause materials to crack and break away from each other.
I have been using Epoxy instead of Polyester resins in many situations when it comes to sealing the top side of my photo fresco pieces. The epoxy may expand and contract more easily than the stiffer polyester resins, although the resins may bond and seep into spaces better. The setting time for the polyester is shorter, but the smells are more annoying. I prefer the polyester resins to the epoxy when it comes to casting detail and strength, but I think when it comes to sealing an outside piece the epoxy, without any layers of resin works best. The thickness of the clear epoxy layer also seems to work like a clear plywood that bonds the exterior edges.
It takes a long time for the epoxy to set up and the air bubbles are problematic, as well as, bugs, debris of any kind and paint brush hairs. Everything will show up in the end. However, with the epoxy I can use the final layer as a part of the structure and reduce the depth that is required for strength. However, the protection against Ultra Violet radiation, UV, is limited with Epoxy and I have gotten yellowing very quickly once I have exposed my pieces to daylight.
I found that the epoxy seems to bond well to portland based cement products and gypsum based plaster products, considering that both of these are porous on the surface and the epoxy has a long set time that allow is to migrate into any crevice that may help with bonding. By using epoxy on the cement and plaster castings I have now had to put a final varnish cost to protect from UV exposure. To me this is the weakest link and requires additional work with drying time, blurring and the basic problems that come with varnishing. I have heard that there may be some kicker that can be added to epoxy to increase or add UV protection to epoxy, but I haven't work with spending more money on that yet.
Assuming that epoxy and clear coating varnishes don't add anything other than new layers of invisible protection and exterior strength to a piece I have gone backwards to find more durable products that don't require coating to exist for a long time outside. This brings me to my next issue about Gypsum Plaster versus Portland Cement.
Water resistant, water proof and ultimate durability go hand in hand. The most toxic element in regular outside exposure is water, through mist, fog, rain, and basic humidity. Temperature change is also an invisible factor that changes the shape of items throughout a day. Strength within an item may resist the shape-shifting, but the porosity of an item also allows saturation which in turn may cause materials to breakdown. Sealing a piece is also a way to stop water from getting into an item, but my understanding is the if an item is completely sealed temperature changes will still make the materials that are used increase and decrease in size throughout a range and this is what can cause materials to crack and break away from each other.
I have been using Epoxy instead of Polyester resins in many situations when it comes to sealing the top side of my photo fresco pieces. The epoxy may expand and contract more easily than the stiffer polyester resins, although the resins may bond and seep into spaces better. The setting time for the polyester is shorter, but the smells are more annoying. I prefer the polyester resins to the epoxy when it comes to casting detail and strength, but I think when it comes to sealing an outside piece the epoxy, without any layers of resin works best. The thickness of the clear epoxy layer also seems to work like a clear plywood that bonds the exterior edges.
It takes a long time for the epoxy to set up and the air bubbles are problematic, as well as, bugs, debris of any kind and paint brush hairs. Everything will show up in the end. However, with the epoxy I can use the final layer as a part of the structure and reduce the depth that is required for strength. However, the protection against Ultra Violet radiation, UV, is limited with Epoxy and I have gotten yellowing very quickly once I have exposed my pieces to daylight.
I found that the epoxy seems to bond well to portland based cement products and gypsum based plaster products, considering that both of these are porous on the surface and the epoxy has a long set time that allow is to migrate into any crevice that may help with bonding. By using epoxy on the cement and plaster castings I have now had to put a final varnish cost to protect from UV exposure. To me this is the weakest link and requires additional work with drying time, blurring and the basic problems that come with varnishing. I have heard that there may be some kicker that can be added to epoxy to increase or add UV protection to epoxy, but I haven't work with spending more money on that yet.
Assuming that epoxy and clear coating varnishes don't add anything other than new layers of invisible protection and exterior strength to a piece I have gone backwards to find more durable products that don't require coating to exist for a long time outside. This brings me to my next issue about Gypsum Plaster versus Portland Cement.
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