Use of Fumed Silica as an aid in alt process printing. Platinotype.

[Robert Hall]

Just a quick pictorial editorial on the use of fumed silica to enhance the max black and improved contrast in printing.This has been found to improve most hand coated processes. Your mileage may vary. Here is 8 ounces of Fumed Silica. It's in a gallon jar and looks to be quite enough to last a lifetime. I got this from Amazon for about $20 including shipping. I would suggest getting a more manageable amount at Bostick and Sullivan. This is enough to last a lifetime as it takes very little to do the job.

I use a high grade 4" foam brush. I dip the brush in dry and allow it to pick up enough silica to stick to the brushes tip. As you can see below, I dip as far as it shows here.

I just kind of poke it in to the silica in order to coat the brush. The image below shows about how much I need to coat the paper.

It looks like this when I have enough on the end. It doesn't take much. I coat the paper carefully to make it as smooth and thin of a coating as I can.

Then I do it a second time. I brush it on the paper, trying to keep it from creating dust and keeping the smaller particles from making a mess. This can be brushed off with the foam brush or just tap the paper lightly on the edge to knock it off.

I keep the lid on as this is very hygroscopic, but not to worry as the material may also be used in solution. I've not done so but Bostick and Sullivan can supply either dry or wet. Your choice.

After the coating I have applied the metals and have to take a small amount of care to make sure the coating is even. Fumed Silica is used as a thickening agent. I find if I use a little more metal solution it coats a bit easier, but I am fairly miserly with the metals to begin with using about 24 drops total to coat an 8x10. I used 100 drops for the 12x20. (50 of metal, 50 of the ferric oxalate), but I use only a little less when I don't use the silica.

Keep the hairdryer out to speed things along. Sorry about the sideways image.

Now here is something I find important. I don't want to get any of the silica on my negatives. I don't know what it will do, but I also don't want to chance it so I lay a 1 mil layer of mylar over the negative. I have to be a bit careful with this as well as it seems to pick up dirt right out of the air. With a little care, one can get a clean piece and cover the negative.

I then lay the coated paper over the mylar like so.

I lock down the print frame and risk another bout of skin cancer to get this less than exciting shot of the print getting exposed in my 1800 watt tanning bed.

I thought this was cool shot showing off my chems on their heating pad. No, one doesn't need the heating pad but it keeps the metals flowing. ( allow me this one, please )

Here is the cooked print awaiting developer to be poured across it. I prefer hot potassium oxalate for its warmer tones.

And here is the final developed image. It develops out instantly and has definite increased max black and improved contrast. If I was more about numbers I would print a step wedge but I like the result so it's good enough for me. Fumed Silica results? Two thumbs up.

[jorj]

Nice summary, Robert.

Word of warning to those ordering this via Amazon: I did too - and was sent hydrophobic fumed silica, even though it was clearly sold as "Aerosil 200" (which is hydrophilic). Cabosil now in hand, I may be able to try again soon...

Moral of the story: stick with Bostick & Sullivan.

[michael9793]

Nice summary, Robert.

Word of warning to those ordering this via Amazon: I did too - and was sent hydrophobic fumed silica, even though it was clearly sold as "Aerosil 200" (which is hydrophilic). Cabosil now in hand, I may be able to try again soon...

Moral of the story: stick with Bostick & Sullivan.

difference in price is 500ml (1/2 Qt)for 19.00 from B&S and Amazon is $12.00 for 5 Qts. I'll take the risk I can order a whole lot of times before I would be loosing my money.