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Old 12-05-2012, 12:08 PM
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Cariboo Bill Cariboo Bill is offline
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Watercolor Lightfast Testing: Preparing Test Sheets

Hi All
Once again take a look at this stuff and see if it is sufficiently clear, follows a sensible pattern and is clear. Now is the time to makes changes, additions and corrections and then we can all work from the same set of rules.

Watercolor Lightfast Test: Preparing the Test Sheets


The following directions are intended to create a standard test sheet that will provide roughly comparable images as we report results of the test. Yes there are a large number of variables such as camera quality, scanner quality, photo software, compression methods, and monitor quality to name a few that will affect our ability to compare test results from uploaded test sheets at the 4 month check points. However if we all have at least similar test sheets and swatches it will make life a bit easier. I am contemplating a report form that might show a sample non exposed swatch and then all of the swatches that have been exposed to light in one image. This will involve cutting and pasting from all the test images and would be easier if all the swatches were more or less comparable.

Setting up the Paper
The standard swatch should be 1" wide and 3" long with the first inch a masstone and the next two inches a flat wash using the standard 1:8, paint to water, dilution. Draw pencil lines vertically one inch apart across the area that will be exposed in the frame. Then draw horizontal lines at 3 inches, leaving about a 1/4 inch between swatches. This will vary depending on the size of paper you are using for the test so pick a spacing that allows you to get the most 3" test patches as possible. At this point it is probably sensible to label each of the test swatches with an abbreviated form of the paint and the color index number for each swatch. This can be done after you have done all the painting as well but my mind likes to have clear directions so I am suggesting that the documentation is done before the painting. People doing a "cut the swatches in half" type of test will need to document each side of the swatch to insure that they can line up the swatches for comparison purposes.

Making the Paint Swatches
It is recognized that pigment is variously affected by sunlight depending on how much "vehicle" (gum arabic for watercolors) surrounds the pigment. Lightfast tests done on a pigment as an acrylic or oil paint cannot be used for comparison becasue the plastic or oil that surrounds the pigment fragments in those mediums provides much more "cover" and in fact both mediums create a continuous color "film" across the canvas. In watercolor, pigment particles can be left sitting naked and alone on the high bumps of the paper. Differences in lightfastness have been reported between a masstone application and a wash application of many pigments and we will want to track that sitution.

In order to insure that the paint dilution is as close to the standard 1:8 dilution we will need to in fact prepare two separate puddles for the paint test. It may well be a good idea to have another painting project ready to go that can use up any of the extra paint!

Masstone paint sample
For this 1 inch of the swatch add sufficient water to the the paint blob, 1 drop or measurement at a time, until the paint reaches a "creamy" texture. This means that a brush drawn through the paint puddle will leave an obvious track but that it will then be filled by the paint. Use that puddle to paint the first inch of the sample. With a bit of practice a reasonably filled 1 inch flat brush can lay down a decent masstone in one stroke and that should be the goal. People doing a two sheet process may need to touch up one or the other sample in order to insure that they are as nearly identical as possible.

Flat wash paint sample
For the next 2 inches of the swatch mix the paint blob and the full 8 parts of water together and once that is done, again lay down a flat wash. A good, full 1 inch flat brush should be able to do that nicely in one stroke as well. For our purposes we want to have that wash as flat and even as possible

Recording and Reporting
Once all the painting is complete take a picture of your test sheet, make sure your name or Wet Canvas name are on the sheet as well as the paint documentation information. This image will be uploaded to the "Watercolor Lightfast Testing Report" thread which is a sticky thread at the top of the Learning Zone. Then you are ready to place that test sheet into the window on January 1, 2013 and the test begins. There will be another set of directions for the timing of checking and reporting changes and the 4 month reporting process. In essence, however, it is worth checking on a weekly basis for the first two months or so in case there are some quick changes. After that checking once a month is adequate. People who are either testing alizarin crimson PR 83 as part of their paints or who have included it as a "control swatch" as Bruce MacEvoy suggests should watch it and when it changes there has been enough exposure to sunlight to make a difference and your test should be examined. Again if you are working within Wet Canvas you will add to the appropriate thread, if you do not want to join Wet Canvas you can email results and observations to [email protected].
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Old 12-06-2012, 01:31 AM
Rcanby Rcanby is offline
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

Maybe I am slow, but I don't follow your statement that we need to make two separate puddles. Do you mean one puddle for the inch of barely-diluted paint for the mass tone sample and a separate puddle for the 2 inch wash of 1:8 dilution? If so, you must intend for us to be extraordinarily precise in measuring that second puddle - it is no problem to measure 8 drops of water but what tool do you use to precisely measure exactly one drop of viscous paint? If it isn't a question of measuring precision, why not just dilute a puddle to mass tone, paint an inch then keep diluting the same puddle until it is ready to be used as a 2" wash (approximately 1:8)?

I apologize if this is a dumb question. Maybe the best direction of all would be a simple step-by-step illustration.
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Old 12-06-2012, 01:46 AM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

Rcanby it is not a dumb question and after thorough discussion we may decide to go with your solution.

To explain first let me say that I think you can squeeze out a small blob of paint from a tube that approximates the size of a drop of water squeezed out of a watercolor squeeze bottle, so getting the fresh paint I think is not a problem.

Here is the issue, you mix up 1 or 2 drops (maybe more for some paints) and do the masstone 1 inch sample, you have removed by that action both water and paint from the test sample. Add 6 more drops of water and you don't really come up with a 1:8 ratio of paint to water. I know that you are right about "how much precision can we really expect" but I think we need to try.

So by starting again with a fresh blob of paint and 8 drops of water we have more chance of having a "standardized" paint swatch across all people who are participating that is the 1:8 dilution. For most paints that dilution comes out somewhere between 1% and skim milk, quite thin and perfect for exposing the pigment fragments to a maximum dose of light. I don't know if your method would create any different a dilution but it worries me.

Fantastic question and we need to work it out. Bruce MacEvoy I think measured everything with real small measuring spoons.
Bill
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Old 12-06-2012, 08:11 AM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

You've thought this out so well, Bill. It's going to be such a valuable resource.

I wonder, in case someone really doesn't know that the point is to expose the strips to as much sun as possible, if it should be mentioned in the instructions... sunniest window, or north window for s. hemisphere, s. window for n. hemi....maybe I just did that, and maybe you've already indicated such.

It's occurred to me that I'm going to run a parallel test making 3 samples of each, hanging a second set of test strips on an inside wall where a painting might hang. Any change might take years, or maybe not, but I'll find out.
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Old 12-06-2012, 01:46 PM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

Sandra good observations, I'll go back and look at the general directions where I think I say something like that but can't entirely remember at this moment. I agree the idea is to have the most light exposure possible but having said that any exposure will be useful if we can accumulate several samples from different people, maybe it will simply take a lot longer. I do really like your idea of setting it up inside where a painting might hang, I am intending to do that as well, though I am not set up for experimenting with flourescent lighting there are indications that it will degrade poor pigments fairly quickly as well
Bill
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Old 12-07-2012, 07:09 PM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

Bill,
The masstone holds no problems and after a couple of test runs the I have sorted a method of getting a decent 1:8 ratio.
In a clean cap from a 5mil paint tube measure out 8 measures of water. Then fill the cap with paint from a tube. The 8 measures of water is then used to clean the paint from the cap. That's about as accurate as you will get and won't use a great deal of pigment.
I am testing under UV glass in an 8x10 frame.
Cheers
Tred
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Old 12-07-2012, 11:30 PM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

One other point Bill. Make sure the printed information on the sheets is done with an ink which isn't going to fade - Noodlers Black or such. Most of us who do pen and wash would have a bottle of this.
Cheers
Tred
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Old 12-08-2012, 08:32 AM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

Thanks for the measuring and especially the point about fading ink!!! Would pencil be safer?
Bill
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Old 12-10-2012, 02:04 PM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

Here's a link to an INK lightfastness test (if the link is broken, you can find it on the first page of the WC pen and ink forum): http://www.wetcanvas.com/forums/show....php?t=1299811
I found it because I was thinking about Tred's concern about fading ink identifying the watercolor test strips, but the test format is an interesting one, too. She just made a long horizontal line of each ink she was testing, identified it on each side, then folded the paper in half vertically and mounted it so that one side of the paper faced the window and the other faced the interior. I'm going to try to adapt that simple fold-in-half technique for my own watercolor testing (no taping, cutting or preparing a second set of samples).

I did a trial run of making test strips last night - 21 yellows and oranges. Bill's instructions are very good but I did struggle trying to get that 1:8 ratio. I tried the small tube caps - couldn't get all the paint out of the caps and had trouble filling them with water 8 times without spills (and extra water). Also tried an ink syringe, which was fine for water but not paint from the tube. I finally eyeballed my dab of paint as "drop sized" and added water drops from a syringe but, while it was definitely much easier, it didn't seem entirely precise. My paint brush wasn't uniformly dry for each strip, so that created some variance, as did the relative thickness of the paint (because my paper was flat). Long story short, I don't think my test strips make the grade; I'll use them for my own testing, but don't think they're good enough for this project. That leads me to the conclusion that we need to make a choice - either we all step back and let the quasi-scientists among us do this project for us or we allow variety and imprecision, hoping the larger quantity of samples will even out the results.

Thanks again, Bill - this is so much harder than it looks!

Rhonda
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Old 12-10-2012, 04:11 PM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

Rhonda I think that you might be too worried about precision. The 1:8 ratio seems to be a "standard" to get a reasonable dilution and give a reasonable swatch of color, but if it ended up 1:6 or 1:10 I don't think that is going to be a huge issue and if we find a problem in 4 months we will look at how we can build a test to specifically test a specific paint that might be unfairly reported.

So yes, I have some hope that we can get a large enough number of participants (a good sample size in perhaps even a statistical sense) and that the problems will even out.

After all, at the end of 4 months, a year, perhaps longer the paints I want to be using are those that have sat in the window in direct light day after day and shown NO changes. Now maybe we have to take another look and think more about dilutions for those that do show changes BUT if there is a paint, aureolin or aliz crimson being likely candidates, that shows major, absolutely no question changes then they are not light fast enough for use by professionals.

So I will be using your second method and will hopefully show it in a set of pictures with the formal launch. I will eyeball a blob of paint that I think is more or less equal to a drop of water from my squeeze bottle. Between mixes I will squeeze out my brush as much as possible with a tissue paper and assume that is good enough. We need a level of precision, yes, but not a scientific one.

Thanks for trying out the system and please consider your sample as part of the project.
Bill
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Old 12-10-2012, 06:39 PM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

Bill,
This 1:8 dilution seems to be the problem area that most of us are having trouble with and I would agree that because of the contours inside a cap from a 5mil tube it is difficult to get all the paint out.
New method.
Squeeze a small pea size blob of paint on the palette. With an eyedropper drop water, drop by drop, counting the drops, into the paint, whilst mixing, until the required consistency for the masstone is achived. Paint the masstone. Then add the required number of water drops to bring the total of drops up to 8 and you have a 1:8 ratio.
Difficult to explain but you get the gist.
Off now to pick up my UV glass.
Cheers
Tred
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Last edited by Tred : 12-10-2012 at 06:41 PM.
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Old 12-11-2012, 03:24 AM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

Thanks Tred, will incorporate that into the directions.
Bill
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Old 12-12-2012, 01:26 AM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

For what it's worth, I did try some test strips in a folded format inspired by the one used on this site for ink lightfastness tests. I prepared a sheet of paper about 13 inches wide by marking it into a series of strips one inch by six inches (two six-inch strips side by side with an inch between them down the length of the paper). I painted each 1 X 6 strip with mass tone on each of the far ends and used every other strip for notes on the paint (1/2 inch would've worked). After I finished painting and marking the full page, I folded both sides back like wings, leaving 3 inches of each sample exposed and 3 inches hidden away. I can later just unfold and compare the exposed and unexposed parts of the samples.

This method probably won't work as well as those identified by Bill for electronically clipping and comparing strips prepared by different people, but it sure makes it easier to prepare and then compare the strips at home.

Rhonda
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Old 12-16-2012, 10:38 AM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

Sorry people I have had an elderly family member in need of a lot of care AND my compute crashed and I haven't been able to get much of anything done. I will do an official post of the directions early next week, I'm glad that we decided to start the testing as of Jan 1 2013.

A couple of updates:

1. Yes Rhonda I think your method would work the only issue there will be to insure that light can't leak in through the edges of the folded paper.

2. "Continuous Entry": I would really like to get a lot of people doing this and it is clear that we won't have a huge number ready to go in January. So I think we will add to the directions so that people can jump into the project over 2013 (when they find out about it probably) by setting out their test pages at the beginning of any month. The key will be to keep track of the amount of light that hits a test sheet and compare the same lengths of time.

Our thinking, based on MacEvoy's directions is that 4 months is a good length of time to provide natural light exposure and expect to see some results, so people who start on say March 1 2013 won't be included in the 4 month comparisons until the end of June. We will keep the test going through 2013 and into 2014 to accumulate all of the people who began testing in 2013 and then evaluate if we want to keep going then.
Bill
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Old 12-16-2012, 08:31 PM
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Re: Watercolor Lightfast Testing: Preparing Test Sheets

I've just opened a test page I've had in my window for over a year, I put tape on the glass of a picture frame in strips so that the wider strips of color were half exposed and half covered. Any exposed writing, though, faded away! I'll write info on the back next time. The only problem here is that there is very little sun at this time of year, but I will try to join in with this test Jan. 1.
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