The Trees of TATMR

In what could be described as our first technical article, we'll explore the behind-the-scenes construction of the trees featured in Thomas and the Magic Railroad!

C ommenting on the model sets of Thomas and the Magic Railroad, in Don Angus' article, cinematographer Robbi Hinds had this to say:

“Building miniature sets is a highly specialized function; for instance, the miniature trees were made specially in London out of brass and then painted, and they look absolutely real"

We managed to track down the London-based company who were contracted to build the trees. 4D Modelshop’s Managing Director, Zyg  Jarzembowski was very happy to share with us what made these trees so special. As you will learn, the manufacturing process that 4D employed is just as fascinating as the final product!
During the spring of 1999, 4D Modelshop received specifications for building assorted scale model trees to be used in the movie.  Approximately one dozen of these customized brass trees were to be constructed and shipped to the Studio 24 West at 940 Lansdowne, Toronto, where the movie’s model shoot was taking place. The lot consisted of four each of large English Oaks and Silver Birches, and four medium-sized Silver Birches1.  The one requirement was that they were to be constructed out of brass. As Zyg explains:

“The reason that the models were made of brass was predominantly for rigidity during transit and whilst on set being filmed.  In addition, so as not to warp or melt in the intense lighting during the filming.  And of course for realistic super detail when using ‘close up’ photography.”

The Artwork and Design Master

The process begins with 4D’s Graphics Designer drawing scaled and varied representations of the tree trunks, branches and foliage using CAD (Computer Aided Design) software. With the desired tree type and size in mind, the design master layout is fit to the dimensions of a brass sheet, for example 12" x 18". CAD permits that strategic positioning of the graphics on the layout to minimize brass wastage.
For the larger oak trees, the artist drew a series of individual leaves to mimic the various, yet distinct foliage shapes and sizes that can be found in nature.

Oak leaves used for design master layout
Color-coded individual oak leaves to be used in design master layout.

Two colors were used in the creation of the design master for the trees: red and black. As you will see, each color serves a specific purpose in the next step for creating realistic-looking foliage.
The ‘black’ areas represent where the brass is to remain intact during the acid etching process. ‘Red’ areas represent where ‘half-etching’ is to take place – that is where only of the brass sheet’s thickness is to be dissolved by the acid from the top of the brass sheet. In the design master, ‘white’ or transparent areas represent where the brass is to be completely dissolved. Using the oak leaf example above, the post-etching result will be a recessed leaf with proud veins.
The leaf templates were used repeatedly by the graphics design artist to lay out foliage individually and at random along the tree branches and fronds, as can be seen in the diagram below.

Partial view of oak design master.
TATMR Oak Tree Design Master: Note random yet strategic layout of the oak foliage on the branches.

The Phototools

Once the artist was satisfied with the template’s 2D layout for the tree, the design master is used to produce two phototools on a photoplotter. One each for the front and reverse side of the brass sheet. The colors used in the design master determine what features appear on each respective phototool, which could be considered to be a sort of photographic ‘negative’ of the design master. In the example below, a magnified portion of the Silver Birch design master demonstrates how it is transformed into a set of phototools.

How the MagicSilver Birch phototools are designed.
Step 2: How the design master's colors determine the layout of the phototools.

Phototool registration marks ensures alignment.
Phototool registration mark

Phototools are used as a template that can be used repeatedly to mass produce the individual components that make up a tree.
Corresponding registration marks are included on both ‘front’ and ‘back’ phototools so that they will line up properly against the brass sheet during the phototool exposure process.
The use of registration marks prevents the phototools from being out of alignment in the phototool machine during the exposure process, which would otherwise result in imperfect components being produced.

Additional examples of the Magic Railroad tree phototools

(Right) The ‘front’ phototool for the Silver Birch foliage, designed to fit on a brass sheet approx. 12” X 13” in size, and .008” thick.
Front phototool for Silver Birch
click image for full size

Phototool of Silver Birch trunk & branches
click image for full size

(Left) The main stem and branches ‘front’ phototool for the 18” Silver Birch tree. The phototool that was used on the reverse side of the brass sheet is identical. The brass sheet’s dimensions are 18 inches long by 12 inches wide. The brass sheet used is also a little thicker (0.012”) to provide robustness.

(right) Set of ‘front’ and ‘back’ Phototools used for the larger oak trees manufactured for the movie.

Set of phototools (front & back) for TATMR oak
click image for full size

Preparation of Brass Sheet

Before transferring the design onto the brass sheet with the phototool, a brass sheet is first prepared by cleaning, then coating both sides of the metal with a liquid photo-resist which dries into a greenish film or emulsion. The ‘negative’ photo-resist is light-sensitive and will chemically change when exposed to the ultra-violet (UV) light of the phototool machine. This means that transparent areas of the phototool will be chemically altered when exposed to the UV light.

Phototool Exposure

The ‘front’ and ‘back’ phototools are inserted into the phototool exposure machine and lined up using the registration marks. The ‘back’ phototool is inserted into the phototool machine reversed. The treated brass sheet is then inserted and secured. The machine is turned on whereupon the UV light performs its work as described in the previous section.
For this example, we’ll use the foliage for the Silver Birch to be transferred onto a prepared brass sheet 12” X 13” in size, and .008” thick (see diagram below).

Transfering design to brass sheet
Phototool transfer to brass sheet (click image for larger view)

After exposure, the brass sheet is removed from the phototool machine, and rinsed in a solution to wash off the unexposed photo-resist, leaving the brass exposed. The black areas of the phototool blocked the UV light from reaching the photo-resist emulsion. The photo resist that was exposed to the UV light -  the transparent areas of the phototool - has hardened into a protective coat and does not wash off – leaving the perfect outline of the foliage and branches on both sides of the brass sheet (see figure below). The objective is to protect these areas from the acid during the etching process.

Protective coat of photoresist remains on brass
Post phototool exposure (after rinsing) Note green photo resist

Acid Etching Process

The brass sheet is then placed into an acid bath chamber, where acid is sprayed on both sides of the sheet. The exposure is timed @30 minutes, so that the acid ‘eats’ through only approximately half of the sheet’s thickness from each side where the brass is fully exposed. On each side, the hardened photo-resist protects the underlying brass from the acid. Using the diagram above, the brass sheet will be completely dissolved where their extents are identical on each side. The resulting product from the full and half etching can be seen in the photo below.

Post Acid Etching of Silver Birch leaves
The resulting product after acid etching - remnant photo-resist is still visible.

Magnified view of post-acid etched brass sheet.

(left) Magnified view of post acid etching (same area used in the previous examples). Note the ‘half-etch’ relief detail of the leaves.

The remnant photo-resist is then washed away with a solvent, and the components are ready to be passed on to the craftsman for the actual construction of the trees.

Assembling and Finishing the Trees

The final stage of assembling, shaping and finishing the tree is a very intensive and time-consuming process. It did, however ensure that every tree constructed for Thomas and the Magic Railroad was unique from one another. Zyg describes the process:

"The central tree trunk is made from 12thou (0.3mm) thick etched brass using the etching process, with additional branches etched loosely to be soldered onto the main body for even more bulk to the tree."
"The main trunk of the tree had a thick brass rod of 12" soldered onto the main body with at least 4" overhanging as a 'planting spike' with the remaining 8" running up the trunk and being well covered with solder for strength.  All of one side of the tree was covered with solder and worked and distressed with the soldering iron to give form and shape.

"The reverse side of the trunk couldn't be soldered as well, as the front solder would melt and run off.  So the reverse was built up with a combination of Hot Glues.  Finally, both sides were covered with 'Plastic Padding', a filler used in the car repair industry, which allows for carving and impressing of the bark detail."
"The skeleton is then twisted into three dimensions in preparation for the etched leaves to be soldered on."

(Below) 4D Craftsman, Louis manipulating one of the large oak trees (24” tall and wide) that were constructed for Thomas and the Magic Railroad. The myriad individual leaf fronds were all manually soldered onto the branches.
4D's Louis manipulating oak tree that was in TATMR
click image for larger view

 “The etched frond (tree shape) then painstakingly had each individual branch of leaves soldered onto the main armature.  Glue would not suffice, as it then had to be tweaked and bent into a 3D shape and required strength whilst it was being manipulated.”
“The final stage was to distress the trunks and hand paint the thousands of leaves, dry brushing as we went for even more detail”
“Several coats of paint/speckling/dry brushing etc and there you have it.”

Below, the finished Silver Birch tree that stands 18” tall and approx 10” wide.

Silver Birch featured in TATMR
click image for larger view

And finally...

Silver Birches seen in TATMR
4Ds Silver Birches as seen in this scene in TATMR (left), and being upstaged by Diesel-10 (right)

Large oak trees built for TATMR by 4D Modelshop
Henry trundling past a few of 4Ds large oak trees

Thanks and Acknowledgements

We wish to sincerely thank 4D’s Zyg Jarzembowski and Andy Feron for their insight, photographs and support for helping us compile this article. My thanks also to 4D's Ben for his prompt assistance for providing me with a few scans. It was certainly an educational process for which we are very grateful. Readers will undoubtedly appreciate the skills and hard work that went into this contribution to Thomas and the Magic Railroad.  
I would like to also extend my thanks once again to Dave Axford for his recollections of seeing - and admiring these sundry trees :)
All article Photos   4D Modelshop and courtesy to SiF, diagrams and article text by James Gratton.

About 4D Modelshop Limited

4D Modelshop website link

4D Modelshop has an extensive stock of quality model making materials, tools and accessories. They offer a wide range of model making services: acid etching, white metal and resin casting, laser cutting, dry transfers, waterslides and custom scenic builds. 4D also manufacture quality models and accessories used for architectural design, film and television.
You can visit 4D Modelshop in person at their walk-in store located  at The Arches, 120 Leman Street, London, or visit their website.  Post-Secondary Student Discounts are offered for in-store and online purchases. Be sure to check out their sponsored professional model making courses offered at local educational institutions.