To Pre-Shrink or not to Pre-Shrink

[Bwoody]

I would like to ask the group for guidance here. Can you all tell me some of the pros and cons of pre-shrinking tissue before applying to the model frame? So far I have applied the tissue dry and un pre-shrunk, and have had good results, except when layering one color tissue over another. The top layer tends to wrinkle up on me. I use UHU glue stick or diluted Elmers glue. Dope is not an option for me.

Looking forward to reading your thoughts.

Cheers,
Bwoody

[Scott]

I use a glue stick like you.I also put the tissue on dry,then shrink it with water.
If I was going to layer one tissue colour over another,I'd shrink the first tissue
to the frame before applying the second colour on top.(I'm not sure if I under-
stood your question correctly or not).

[kittyfritters]

To pre-shrink or not to pre-shrink, that is the question!

For me it depends on the strength of the underlying structure. I pre-shrink when covering very light structures that cannot stand the stress of shrinking tissue. Sometimes I pre-shrink on selected parts of a model, for example the tail surfaces of the 600 or 900 series models. For models that are a little stronger I apply the tissue dry and shrink with 70% rubbing alcohol. The alcohol does not take all the shrink out of the tissue so if you have a wrinkle somewhere you can apply some straight water with your finger tip or a cotton ball and get more shrink. For stronger structures like a 300 or 400 series model I apply a sealer to the parts the tissue will touch and "wet" apply with damp tissue. This allows you to stretch the wet tissue or silkspan around compound curves and gets an absolutely smooth surface. The caution on that is that you have to use a tissue with good wet strength such as Asuka or Esaki (If you can find some). The Guillow's tissue will work wet if you are well practiced. The structure has to be well sanded and absolutely free of bumps before covering. Tissue applied wet will show every flaw in the structure. There is an excellent tutorial on wet covering by Scigs30 on this forum.

My wife is extremely allergic to dope, even if I am using it outdoors, so I have been using glue stick since 2004 and have no trouble with it even when covering wet. What I watch for is a general purpose, permanent glue stick, nothing labeled "school". The school glue sticks are meant to be extremely washable so that it can be washed out of kids clothes. If you use a "school" glue stick and take the model to the flying field on a morning with a heavy dew the tissue will come off. To seal the balsa before covering wet I use a diluted water based clear finish. I fix tissue with Krylon, UV resistant artists fixative #1305 for gloss finish and #1311 for matte finish. These are compatible with acrylic paints and inks for airbrushing and Design Master spray paints although I try to do all my color trim with tissue wherever possible.

Hope this helps.

KF
(Howard Littman)

[collinmccallum]

tissue manufacturing process is interesting... machine breaks up fibers, adds water, becomes pulp, pulp is extruded evenly under a hot roller, the fibers in the pulp are naturally squished parallel to the direction the hot roller rotates, creating horizontal grain runs, the hot roller pushes out most of the water and maintains correct thickness, it then passed through a hot air/drying chamber and is rapidly shrunk before being wound on large rolls, then off to the slicer...

as far as wrinkles go what i do is glue down the 2nd layers perimeter edges with un-diluted Elmer's glue, when fully dry, apply ez dope over and into both layers at the same time... tha gives the 2nd layers edges something to hold onto and then they shrink in unison. much respect! -collinmccallum