Bleach Formula Questions
I've had mixed results bleaching posters with what I think is a 0.05 calcium hypochlorite Ca(ClO)2 solution. I dilute calcium hypochlorite (68%) by mixing 2.0g with 1000ml distilled water. I know I need to get better at understanding the math (dilution rate is based on Ca(ClO)2 strength) but I'm thinking I'm ranging from a 0.03 to 0.05% solution.
I spray a liberal amount of the bleach on both sides of the poster. The poster rests in the solution for five-minutes between Mylar sheets. I rinse using tap water (our water is somewhat hard) and then I wash both sides with Ca(OH)2 followed by a final rinse with distilled water.
For those of you more experienced with bleaching, can you check my dilution math and/ or perhaps offer the mix you're using (grams per ml water)?
In some cases, results are satisfactory with the mix I'm using. In other cases, especially those with fairly decent toning, I only see marginal lightening of the toned areas. Colors/ ink generally improved as expected.
I'm wondering if my solution is too weak or if I need to prolong the bleaching time from five-minutes to 7-8 minutes based on poster condition.
As always, thanks in advance for your thoughts and comments!
I spray a liberal amount of the bleach on both sides of the poster. The poster rests in the solution for five-minutes between Mylar sheets. I rinse using tap water (our water is somewhat hard) and then I wash both sides with Ca(OH)2 followed by a final rinse with distilled water.
For those of you more experienced with bleaching, can you check my dilution math and/ or perhaps offer the mix you're using (grams per ml water)?
In some cases, results are satisfactory with the mix I'm using. In other cases, especially those with fairly decent toning, I only see marginal lightening of the toned areas. Colors/ ink generally improved as expected.
I'm wondering if my solution is too weak or if I need to prolong the bleaching time from five-minutes to 7-8 minutes based on poster condition.
As always, thanks in advance for your thoughts and comments!
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Here's the basic description (search the site for more detail) for the mix:
Measure out 2g of the powder on the scale and mix with 1 liter of deionized water. Let it sit overnight, preferably 12 hours so the solution can reach equilibrium. This one liter of solution is concentrated and will need to be diluted by another 1 liter of water. Any of the CaOH that doesn't mix with the water is basically still powder and settles at the bottom - I gently stir up the top part of the solution but leave the particulates at the bottom. Then I gently poor the mixed solution into the new container (leaving the remaining solid at the bottom) and then add the additional 1 liter of water. After you mix the solution a bit more it is ready to use.
To deacidify, I use the "Mylar sheet" method.
I place the poster face up on a sheet of Mylar and using a dollar store, Lowes, Home depot spray bottle, I douse (and I mean douse) the poster with the Ca(OH)2 mix. I place another sheet of Mylar on top of the side of the poster I just sprayed (the poster is now in a Mylar "sandwich").
Next, I flip the poster, remove the top Mylar sheet and and spray the other side (back side of the poster).
You'll see folds and creases start to relax. While you can do it later, I VERY GENTLY start to work out the folds, creases, etc. Again, be very gentle, when the paper is this wet, it tears easily. I work out the creases and folds from the back side because it's easier for me to see the fold lines and creases.
After I work out the major creases and folds, I place the Mylar sheet back on the poster (it's now sandwiched between Mylar sheets again) and I let it rest for 30-minutes.
After 30-minutes, I rinse the entire poster thoroughly using tap water. My water is somewhat hard. It acts as a buffer.
You'll find other ways to do deacidify here and on other sites. This method works well for me. As other know, the deacidification process does a fair job at removing dirt, small stains, etc. and generally brightens up a poster while protecting it as well.
You'll find the poster sticks to the Mylar.
After I've worked out all the major creases and folds, I carry the poster (it's still clinging to the Mylar) over the the mounting board (I've already applied the wheat paste). Next, I roll the poster out very slowly onto the board making sure I don't create any new folds or wrinkles.
You may end up with some small air pockets or wavy areas of the poster when it's on the Masa. Once I have the poster completely on the board, I place a CLEAN Mylar sheet on top of the poster and from the center of the poster to the edges, I work the air pockets, small ripples and excess wheat paste out to the edge of the board.
As I've mentioned, you'll see Posterfix Chris use sponges and/ or squeegees directly on the poster to ensure all the air pockets are removed and the poster if flat to the Masa. I've never had success with this technique. The ink smears when I've tired it - especially on a poster that's been bleached.
That said, the process I described works well for me. I've seen some spray down Masa or a poster and just walk it over to the mounting board. There's a number of techniques used to mount the poster to the board and a number of ways to remove air pockets and such. I've found one of the keys to this is to develop a process and technique and work to continuously improve it. I hacked up a few posters but they were cheap since I had to go through the learning curve like others here (am I'm still learning).
Follow Charlie and Mark's tips and ping them for advice. They've always been quick to help me.
*allow a poster to dry to about 75/80% dry before applying the adhesive and laying the poster down on the masa; otherwise too much water creates more noticeable fold lines which is everything when laying down one sheets.
hie are holes filled?
Thank you