Gum won't come off

[Nicole Hagesteijn]

Hi,
I am totally new here. Also new at gum printing.
I followed a workshop and started with Christina Anderson's book as my big help. But despite her wonderfull troubleshouting section I cannot solve the problem I encounter.
I make my coating from arabic gum lumps. With nylon stockings. I use tab water as I was told during the workshop, though I read that some prefer distilled water.
my coating has the right viscosity 14-17 Baume, I use gum : K bichr : water= 3 : 2 : 1 and I determined exposure with a Stouffers stepwedge. Strange enough I calculated 7 seconds for my gum and 8 minutes for my cyanotypie.

my gum won't come off, my cyanotypie is beautifull

what can be the problem? Anyone any idea?
thanks!

 

[fotch]

Hello Nicole and welcome to APUG. Someone with experience will reply soon I expect. Good luck.

 

[Sirius Glass]

Welcome to APUG

I cannot help you but someone here will jump in soon. Hang in there.

 

[pschwart]

I print primarily carbon transfer, but I think gums are subject to some of the same problems. A 7 second exposure is extremely atypical. If your gum is not washing out, something besides exposure must be hardening the gum. It could be dark effect, or something else that is causing the gum to spontaneously harden. Review your workflow. Things that can cause problems: sizing/hardening; not using papers immediately after coating; and incompatibility of some pigments.
How were you able to determine a base exposure if your gum is not washing out? It's not a bad idea to mix your dichromate stock using distilled water.
Sorry I can't be more help. If you post on DPUG you might get an experienced gum printer to weigh in.

 

[Nicole Hagesteijn]

Reading stouffer when gum won't come off

Thank you very much for your answer. A week ago the gum came eventually off, overnight, ugly and difficult to read the stepwedge. Now, the gum solution being a week older again ( which makes it now about six week old) it won't come off at all anymore. This morning I added water instead of Kbichr and coated a strip of sized paper. I did not expose it, when it was dry, but put it into the water immedeately. It did not come off. Then I took gum solution that I stored for 6 weeks without pigment, added pigment and repeated the experiment. Now some pigment came off, but it took more time then one would expect without exposure.
so I wonder if there exists something like inapropriate gum, or gum that hardens with a specific pigment, whereas another gum won't? Are Ther Some pigment vehicles that don't match with gum? ( I used indanthrene blue and transparant yellow from Winsor)

 

[pschwart]

Thank you very much for your answer. A week ago the gum came eventually off, overnight, ugly and difficult to read the stepwedge. Now, the gum solution being a week older again ( which makes it now about six week old) it won't come off at all anymore. This morning I added water instead of Kbichr and coated a strip of sized paper. I did not expose it, when it was dry, but put it into the water immedeately. It did not come off. Then I took gum solution that I stored for 6 weeks without pigment, added pigment and repeated the experiment. Now some pigment came off, but it took more time then one would expect without exposure.
so I wonder if there exists something like inapropriate gum, or gum that hardens with a specific pigment, whereas another gum won't? Are Ther Some pigment vehicles that don't match with gum? ( I used indanthrene blue and transparant yellow from Winsor)

Gum can spoil, but I'm not sure how it behaves when it does. I would expect there are some pigments that contain ingredients that can spontaneously harden gum. This is rare, but it can happen with gelatin when making carbon transfers. It does sound like you are having a problem with your materials. Time for a test plan, changing *one* thing at a time in order to isolate the culprit. My suggestion: start with a NEW batch of COMMERCIALLY prepared gum, and use the same pigments. If that doesn't solve the problem, switch to some pigments that can vouched for by other gum printers. Christina has documented some pigments to use; I'd select from those. I am guessing the trouble will be resolved at this point. If not, time to take a detailed look at the rest of your workflow.

 

[pschwart]

I see Winsor Newton indanthrene blue (PB60) and transparent yellow (PY150) are on Christina's pigment list. I would definitely test using a commercially prepared gum before switching pigments.

 

[Nicole Hagesteijn]

Changing gum

Indeed I decided to change gum and not pigment. I have been reading about gum today and have seen pictures of hashab gum from acacia Senegal as opposed to lesser quality gum. I probabely have lower quality gum judging from the look of it, but also the fact that dissolving 300 gr in 1 liter water gives a viscosity >>> 50 Baume. I need to add water untill I have more than 2 liters gum in order to get the 14- 12,5 Baume that is apropriate for gum printing. I thought this did not matter, because it would be the viscosity that counts, but probabely this is a wrong conclusion. I ordered new gum and hope to succeed in making a print next week.
I want to thank you very much for thinking along with me to solve the problem.
When I reach a final conclusion about the gum I will post again.

 

[pschwart]

I think the new gum will resolve this issue -- when your materials start behaving in unexpected ways, it is usually best to stop and figure out what is going on.

 

[ced]

Get some artist's gum arabic like a small bottle from Winsor & Newton.
http://www.winsornewton.com/row/sho.../gum-arabic-2-53-us-fl-oz-75ml-bottle-3021763

 

[Mainecoonmaniac]

Is it over exposed? Try the same gum emulsion on the same paper dried, but unexposed. Hopefully, all or most of the gum should dissolve from your paper when you "develop" your gum print. If not, you have problems with your gum emulsion.