Re: Gum problem(s)

P.S. I've searched for information about the UV output of the
photoflood bulbs is, and someone else on this list also tried to get
this information, without success. Either we haven't found the right
people to talk to or the right places to look, or that information
simply isn't available. If someone knows, I'd be most grateful. Like I
say, all I know is that it makes great gum prints for me,
Katharine

On Nov 18, 2005, at 12:16 PM, Yves Gauvreau wrote:

> Not more tungsten then a photoflood Kate, the thing is that a gum
> dichro
> matrix probably respond to light in a relatively broad manner with
> peaks and
> valleys from relatively invisible UV light up into the visible light
> area
> and I could say the same for most source of light but the peeks and
> valleys
> would be more in the visible range. The exception would be laser which
> have
> a very narroe spectrum. I asked the question earlier about this and
> the
> answer was that the highest peek was around 350 nm which is in the UV
> range
> and if I'm not mistaking it is just a bit below visible light
> (violet). I
> suspect that a photoflood light gives out a significant peek in a
> region
> where the dichro as also a peek maybe those corresponding peek are not
> as hi
> as the 350nm one but I'm sure they are significant (hi) enough that the
> dichro become insoluble which is what we are looking for. At 5 to 10
> bucks a
> piece they are a real bargain.
>
> Based on what I've learned so far and if I can find out the level of
> relative humidity that give the highest speed or shortest exposure time
> using a photoflood bulb I don't think someone could convince me to use
> anything else. I must add that I can use my shower to get the optimal
> RH
> level, ain't this fun????
>
> Regards
> Yves
>
>
>
> ----- Original Message -----
> From: "Kate M" <kateb@paradise.net.nz>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Friday, November 18, 2005 2:37 PM
> Subject: RE: Gum problem(s)
>
>
>> But isn't photoflood a tungsten light source? There would be very
>> little
> uv
>> output then, a lot of heat though.....when ever I've done copywork
>> under
>> photofloods, I've used tungsten film.
>> Kate
>>
>> -----Original Message-----
>> From: Katharine Thayer [mailto:kthayer@pacifier.com]
>> Sent: Saturday, 19 November 2005 4:31 a.m.
>> To: alt-photo-process-l@sask.usask.ca
>> Subject: Re: Gum problem(s)
>>
>>
>>
>> Yves,
>> Thanks for description.
>>
>> Okay,, this sounds like (1) pigment stain (not clearing in masked
>> areas) and ... (2) ... hmmm, I'd need to see the print, I think. Your
>> description of not much pigment in exposed areas sounds like
>> underexposure, but 20 minutes under a photoflood is a very long
>> exposure. My exposures are from 1 to 5 minutes with the same kind of
>> light; most exposures are 2 or 3 minutes. But if you live in a very
>> dry
>> climate, you may need a longer exposure, as there is almost a vertical
>> inverse relation between humidity and time required for hardening.
>>
>> Katharine
>>
>>
>> On Nov 17, 2005, at 6:30 PM, Yves Gauvreau wrote:
>>
>>> Hi all,
>>>
>>> I tried a few variants in the pigment / gum ratio and coated to
>>> different
>>> tickness directly on paper using various exposition times. None of
>>> the
>>> combination I've tried cleared to the paper in masked areas. Also I
>>> tried
>>> this with one dark brown watercolor paint tube and one using a dry
>>> pigment
>>> (dark brown also). I use a 1:1 ratio of pigment/gum and saturated
>>> pot.
>>> dichromate solution.
>>>
>>> I also notice the unmask area don't hold much if any pigment either.
>>> It's
>>> like some pigments get into the paper causing a noticable darkening
>>> and
>>> almost none stays on top of the paper in insoluble gum. My last
>>> attempt was
>>> 20 minutes exposure under a #2 photoflood light.
>>>
>>> Any suggestion on what is the problem(s) and what I should try next?
>>>
>>> Thanks
>>> Yves
>>>
>>> PS Both pigments I used seem to be of the opaque type if this could
>>> help.
>>>
>>
>>
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>
Received on Fri Nov 18 15:03:50 2005