Inside the Collection

The conservation of a transistor radio

Transistor radio, flower basket by Toshiba 1957
96/43/1 Transistor radio, flower basket, , Toshiba, Tokyo Electrical Company Limited, Japan, 1957; Collection Powerhouse Museum

A transistor radio, designed as an ‘oriental’ flower basket by Toshiba in 1957 for the western market, recently came to the conservation lab for treatment. It is made of cream and red plastic with a chrome handle and it has a radio and speaker inside. From the outside, the radio seemed to be in reasonable condition so conservator, Vanessa Pitt gave it a surface clean. She wanted to remove the dust that could be seen through the slats in the base of the radio.

When she took the radio apart with the help of conservator Carey Ward, the treatment process became much more complicated. The radio contained four AA batteries that had been left in for a long time. The batteries had corroded and the leaking battery acid had caused a lot of corrosion to the radio’s internal metal structure and left grimy yellow deposits on the plastic.

Inside the transistor radio, detail of batteries
Removing the battery bracket. Two of the leaking batteries inside the radio

The batteries were taken out, photographed and disposed of. The radio needed to be deconstructed so that the corroded metals could be stabilised. Many photos were taken which showed how the wiring connected and was essential for the reconstruction process.

Removing the battery bracket from transistor radio
Removing the battery bracket.

The metal battery bracket was screwed into the red plastic body, so this was easily undone. The speaker was attached to the battery bracket with wires and soldered areas. These needed to be taken apart so that the bracket could be treated separately. Carey removed the solder to release the necessary wires.

Detaching the wires and details of the corrosion transistor radio
Detaching the wires and details of the corrosion

Conservator Carey Ward treated the bracket by using a plastic grit machine to remove the corrosion. This is similar to a sand blasting machine but is gentler and the pressure can be reduced.

Although the corrosion looked alarming, it was mainly on the surface. When as much corrosion as possible was removed, the metal was treated with kethos solution. This converts corrosive ferrous irons into stable ferrous phosphates and stops the corrosion process.

Corrosion being removed from the bracket in the plastic grit machine and Kephos solution stabilises the damaged metal
Corrosion being removed from the bracket in the plastic grit machine and Kephos solution stabilises the damaged metal

The speaker had a lot of corrosion and hard battery acid residue on it. Petroleum spirits as well as careful work with a scalpel were used to reduce the corrosion and residue. The top panel of the radio interior was in reasonable condition, but it did have a small deposit of acidic white chloride crystals coating one of its metal components. The acid from the crystals had removed the original surface coating. Vanessa used petroleum spirits and a scalpel to remove the crystals and then sealed the surface with Paraloid B72 in acetone.

The speaker, white crystals coating the metal and after treatment
The speaker, white crystals coating the metal and after treatment

The lower red plastic body was dusty, and hardened, grimy yellow deposits from the battery acid coated the inside of the bowl. The area was brush vacuumed, and the hardened deposits removed with cotton buds and distilled water and a small amount of Triton X-100 detergent. The composite cardboard that the speaker was attached to was removed and brush vacuumed.

Grimy deposits inside the bowl
Grimy deposits inside the bowl

Carey and Vanessa re-constructed the radio, re-soldering where necessary. The radio will be part of the Oopsatorium exhibition that will be travelling next year. As a follow up to this treatment, Vanessa plans to check other objects in the collection that are battery operated to make sure they don’t contain any nasty surprises.

The inside of the conserved object.
The inside of the conserved object.

2 responses to “The conservation of a transistor radio

  • Tell me, what is ‘kethos solution’?

    I see it mentioned in the restoration of the transistor radio thus “Although the corrosion looked alarming, it was mainly on the surface. When as much corrosion as possible was removed, the metal was treated with kethos solution. This converts corrosive ferrous irons into stable ferrous phosphates and stops the corrosion process.”

    Appreciate your response.

    David

    • Hi David,
      Apologies for the delay – I’ve been away for a while.
      Kethos solution is a phosphoric acid that converts iron oxide (rust) to iron phosphate which makes it neutral and inhibits corrosion. We used a solution that we’ve had for a long time so I’m not sure if you can buy it still. You can buy it in a paint solution. We have used Feronite Rust Convertor in the past successfully and are currently doing some more experiments on it. This is a water based solution that uses tannic acid to convert the rust. I can let you know the results of our experiments if you’d like.
      Kind regards
      Kate Chidlow

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