Topic: What type of paper is this?

[daron]

This is for the old guys. I've begun working at a university. My job is to go through all the drawings in the flat files which date as old as 1908, organize them and put info into a database. The question is this; what do you call the paper that was printed on the back side to show up on the front? The paper looks like a mix between mylar and vellum, but is thicker, brown (probably due to age), and if you put the slightest crease in it it leaves a white mark, similar to plastic. What is this stuff? Sorry, no picture.

[M-dub]

We've got tons of that stuff here...
I've always just assumed it was a heavier mylar... No?

[daron]

No idea, but it's awful stuff. I have to flip the paper and read it backwards just to be able to really see what I'm trying to read. I guess it's not THAT old since it was still in use in the '90's, but I also have one from '75, then there's about 60 more file drawers I have to go through. Who knows? For the curious, yes I have already seen some linen drawings here.

[mjfarrell]

This is most likely a Diazo reprograpic process on "film", this type of photo-mylar came in two flavors rough on both sides, or rough for inking on the front and slick on the back.

[daron]

Diazo prints. I've heard that before. That's probably what it is. I just checked and it looks like I may have both types you mention. The rough on both sides has the feel of a thin paper bag and the the slick is the one that shows the creasings and both are printed in reverse so as to make the slick side the front and not the back. I've even seen a sheet where someone had to make a quick revision and had to write backwards. That was funny.

[daron]

BTW, Thanks MJ.

[mjfarrell]

I wouldn't be surprised if it has holes in the top for Pin Bar registration.
What you hold in your hand is an ancient form of XREF.

[Chuck Gabriel]

Sounds like sepia paper.

[daron]

Looks like sepia, but I think I'll go with the diazo, at least until someone here tells me otherwise. I'm sure my boss knows what it is, but he has been in meetings most of the day.

Ancient form of xref. Funny. I'm sure it's true though.

[deegeecees]

... What you hold in your hand is an ancient form of XREF.

The "Overlay" type.

 

[T.Willey]

... What you hold in your hand is an ancient form of XREF.

The "Overlay" type.

 

Ones that I worked with would have been the 'Attach' type since we drew on the back of them with our items when I worked for an Electrical Engineer.  The ones we had were 'Reverse vellums'.

[deegeecees]

... What you hold in your hand is an ancient form of XREF.

The "Overlay" type.

 

Ones that I worked with would have been the 'Attach' type since we drew on the back of them with our items when I worked for an Electrical Engineer.  The ones we had were 'Reverse vellums'.

I've seen those, but never had to touch em. I used to do a lot of conveyor/plant work, mainly food industry, so before Cad, there were these vellums that were in terrible shape from constantly shifting plant machinery, we'd have to snake some conveyor through this mess, so we'd use the vellums of the plant overall plans, and elevations (when available) to draw over.

[Guest]

Looks like sepia, but I think I'll go with the diazo, at least until someone here tells me otherwise. I'm sure my boss knows what it is, but he has been in meetings most of the day.

Ancient form of xref. Funny. I'm sure it's true though.

Having been a "blueprint boy" for 2 +/- years, I would have to agree with Chuck.  The sepia paper has one side that can be erased (but not too much or you'll wear a hole right through the paper).  A typical diazo print is/was done on the bright yellow paper that is sealed in the thick heavy black plastic to keep light out - you leave it out in the light too long and it's useless.  You would put the original plot (usually done on mylar or a thinner paper) on top of the yellow diazo paper and when they were put through the blueprint machine any yellow that wasn't covered by the linework from the original plot was essentially "burned off", leaving the paper white and the lines blue.


As a side note, paper cuts and ammonia do NOT play well together.   

[CADaver]

I'm going with Matt and Chuck on this one, the white crease is a giveaway.

[Dinosaur]

It is undoubtedly sepia paper - name derived from the brownish color of the finished copy - an original was run reversed through a diazo machine with the line work against the photo sensitive emulsion side and a very good vellum surface to work with was provided on the other.  If one was careful when running the first sepia, a second with additional line work could be run from it resulting in a screened effect.  Erasures were not easy on the "working side" but a light touch on the electric eraser with the right eraser strip would allow 2 or 3 changes in a given area.  There was a vile smelling eradicator fluid that could be brushed onto the exposed emulsion side to get rid of unwanted line work that was burned in with the diazo.  The process with mylar sepia was similar but instead of burning holes in the media one could easily remove all of the "tooth" from the surface leaving a shiny plastic that virtually nothing could stick to.