Bonding (gluing) with cling film (food wrap). IT WORKS!

[Tex]

Howdy Leif!

Here's what I found about grit sizes, those funny numbers, in wikipedia:
(Sandpaper - Wikipedia, the free encyclopedia)

Grit sizes

Grit size refers to the size of the particles of abrading materials embedded in the sandpaper. Several different standards have been established for grit size. These standards establish not only the average grit size, but also the allowable variation from the average. The two most common are the United States CAMI (Coated Abrasive Manufacturers Institute, now part of the Unified Abrasives Manufacturers' Association) and the European FEPA (Federation of European Producers of Abrasives) "P" grade. The FEPA system is the same as the ISO 6344 standard. Other systems used in sandpaper include the Japanese Industrial Standards Committee (JIS), the micron grade (generally used for very fine grits). The "ought" system ({0, 00, 000, ...} aka {1/0, 2/0, 3/0, ...}) was used in the past in the US. Cheaper sandpapers sometimes use nomenclature such as "Coarse", "Medium" and "Fine", but it is unclear to what standards these names refer.

You can find a good chart there, but I can't seem to copy it; the formatting gets lost. Sorry, looks like you'll have to look it up yourself ...
- Tex

[Leif Ohlsson]

Thanks, Tex! So the "120" in "120 grit" refers to the average thickness of the grit particles in thousands of millimeters (micrometer, my), right? Good to know.


Wait for it - ordinary tape, and wide packing tape will work as well!

While using small pieces of ordinary office tape to fix the two parts to be necroscoped together in correct and aligned position, it struck me - what if ordinary document tape works as a necroscoping bonding agent as well? And it really does! This will make life very easy when it comes to necroscoping small parts.

The next line of thought was logical - what if wide packing tape works as well? And it does - although it will make the bond a bit thicker than with cling wrap, plastic bags and other thin sheets of plastic. Here's the process (generally applicable for necroscopy in fact):



Above: Here, one piece of photo paper has been taped over with wide packing tape on the backside.



Above: The two pieces to be necroscoped are placed in the pocket of protective copying paper, and taped in place with two small pieces of document tape at the edges. In this example one layer is photo paper, and the other ordinary copying paper (simulating inner pattern of a fuselage, for example).



Above: Necroscope as usual. But with packing tape you need to keep up the heat quite a bit longer to accomplish even melting of the comparatively thick bonding layer. Heat one side first, turn over, and heat the other just as long. At the left is the coarse sanding paper (120 grit) used for roughing up the backside of the photo paper.



Above: Minutes after necroscoping the part is ready to shape. No delamination.



Above: Thickness of this laminate (180 gsm photo paper + packing tape + copy paper) is 0.25 mm, some 2-3/10 mm thicker than using three layers of thin cling wrap. The slight delamination which can be seen here was cured by re-heating the laminate, and keeping up the heat longer. That's how I learned about the need for longer heating time when using packing tape.



Above: This is a ring made the same way. This time I found (by accidental ommission) that the use of packing tape on the backside of the photopaper eliminates the need for sanding!

Evaluation: The laminate is really thick and quite difficult to shape. But it will shape, and would keep its shape if supported by a former. I wouldn't really like to work with this material, however. Hopefully, I'll be able to keep to more ordinary paper and thinner bonding agents, like cling wrap, plastic bags, and ordinary office tape for smaller pieces.

Leif

[papermate]

As a side note on using photo paper. From my experience, the colours of models built using photo paper will fade in time and will turn completely colourless eventually. I wonder if any one has this experience and would like to share?

Papermate

[Necroscope]

Hi Lief,
Just awesome!
BTW - as far as I know sandpaper 120 meaning that there 120 grits (particles) per 1 square centimeter.

Hi papermate,
nope. It's still looks good after a few years. But I saw some opinions that photo-paper fades under constant direct sunlight for several month(years?).

[Leif Ohlsson]

Glad you're happy with what you've made happen, Denis! - L.

PS. You made me look closer at the link Tex provided: Wikipedia - Sandpaper and at the Grit size table. What you're saying is that "120 grit" actually refers to what I now see is either the "CAMI grit designation", or the "FEPA" or "ISO 6344" standard. 120 (CAMI) seems to mean an average particle size of 115 mikrometers (µm), and 120 (FEPA, ISO 6344) would mean an average particle size of 125 mikrometers (µm).

So, on average, "120" could mean three things, all very close to each other. But that only happens to be true for "120" - for higher or lower numbers, I did not think it through at all - higher grit number means smaller particles, of course. Which, as you say, means more particles per square whatever. Stupid me! Keep educating me, I'm grateful.

[Lighter]

Originally Posted by Necroscope

Hi papermate,
nope. It's still looks good after a few years. But I saw some opinions that photo-paper fades under constant direct sunlight for several month(years?).

Depends totally on paper + ink. Usually (?!?) staying in a brand for paper, ink and printer gives longest results. Information will be on the paper package. Note that longevity might require much more expensive paper and ink than those readily available. The word archival is a hint on a package.

Sunlight is murder on prints no matter how they are printed. Including commercial letterpress products. You won't find a museum with direct sunlight on artwork.

[HMCS]

How does it react to edge sanding

[HMCS]

When I laminate I run a line of thin CA along the edge and lightly sand it,.. It makes the seam disappear or I coat surface with CA and sand down fibers and raised bumps

[Dabeer]

I got to experiment with this technique tonight. I tried to make some metallic paper by necroscoping a mylar emergency blanket to some 160gsm cover stock, and tried getting two printed pages aligned for nice two-sided printing.

My first test used a recycled newspaper bag labeled as LDPE. A full minute of ironing at the highest temp melted the plastic, but it never made a good bond with either the paper or the mylar. The mylar was left quite wrinkled, and probably would not have been printable.

My second test used Wal-Mart brand plastic wrap, and this time I tensioned the mylar before ironing. The resulting wrinkles were less, but still not really printable. The card also curled quite badly once it cooled.

My third test involved two pieces of ~105gsm paper full-page-printed solid black with a few white lines that needed to be aligned front-to-back. I used the Wal-Mart brand plastic wrap. I ended up having to cut into the paper until I reached an alignment mark on both sheets to be able to get them aligned, because they were so dark no light came through, but about 30 seconds of ironing on each side produced a fantastic bond, and left the finished product flatter than it was after printing (the amount of black ink required left the pages significantly distorted).

The finished mylar product was completely unprintable, as there were too many wrinkles, and the mylar separated from the bonding agent.

The finished back-to-back alignment was extremely successful, and after trimming, I was able to color the edges using my Pitt pens without any trouble.

I definitely will be using this technique in the future when laminating is called for. A few minutes of work with a hot iron saves a lot of time over waiting for a time when I can go outside to spray the glue, then rushing to get it under a pile of heavy books, then waiting for it to cure, then waiting for the smell to go away so I can start cutting it indoors. Thanks, Necroscope, for the tip, and for all others for the testing you've contributed!

[Leif Ohlsson]

Good news, Duff! - and another convertite to necroscopianity, I take it? - L.